Search

Abstract The amalgamation of five Paleo- to Mesoarchean protocontinent blocks [Singhbhum, Bastar, Dharwar, Aravalli and Bundelkhand] resulted in the present-day tectonic configuration of India. The Dongargarh Supergroup is a major volcano-sedimentary sequence in the Bastar craton, central India. For nearly six decades, it was presumed that the extensive lava pile in the Dongargarh Supergroup has accumulated over a protracted duration of magmatic eruptions spanning from early Paleoproterozoic (~2462 Ma) to mid-Mesoproterozoic (~1367 Ma). However, in the absence of any age information, this time-window remained speculative. The detrital zircon U-Pb depositional ages acquired for the three intercalated sedimentary units do not provide any such evidence of significantly prolonged magmatism in the Dongargarh Supergroup. The close proximity between the depositional ages and the similarities between the geochemical attributes of the basalts in the four volcanic formations [Pitapani, Sitagota, Mangikhuta and Kotima] of the Dongargarh Supergroup, suggest contemporaneous evolution spanning few tens of million years around ca. 2.5 Ga. The negative initial εNd (t =2.5 Ga) isotopic compositions in the bulk-rock basalt samples of Pitapani (−0.36 to +0.41) and Mangikhuta (−0.62 to −0.49) suggest interaction with ~3.5 Ga continental crust in the Bastar craton. On the contrary, near chondritic to positive initial εNd (t =2.5 Ga) isotopic compositions in the Kotima (+0.01 to +0.92) and Sitagota (+1.75 to +2.24) basalts are inconsistent with any significant crustal assimilation. Overall, the initial εHf (t =2.5 Ga) isotopic compositions in the four volcanic formations are positive and range from +0.31 to +6.26, which is consistent with their generation from juvenile mantle sources. On the basis of Nb concentrations and rare earth element systematics, the basalts in the Dongargarh Supergroup can be subdivided into two geochemical groups comprising of Sitagota + Kotima with Nb < 4.5 ppm, and Pitapani + Mangikhuta with Nb > 4.5 ppm. The Zr/Nb and Nb/Yb systematics in these basalts suggest that their mantle sources were relatively fertile and enriched in high field strength elements, which is comparable to the source region of mid-oceanic ridge basalts, and basalts that are generated in the back-arc basins. Collectively, the Dongargarh basalts exhibit negative Nb and Ti anomalies on a primitive mantle normalized incompatible trace element variation diagram. The geochemical signatures in combination with the initial isotopic compositions in these basalts are inconsistent with their origin in a continental-rift setting, or from a mantle plume, as hypothesised by the previous evolutionary models proposed for the Dongargarh Supergroup. Moreover, it cannot be attributed to crustal assimilation sensu stricto. Instead, we interpret the evolution of the volcanic sequences in the Dongargarh Supergroup by the subduction of an oceanic spreading ridge beneath the continental lithosphere, presumably in a back-arc or marginal sea basin that has witnessed contemporaneous sedimentation, which led to the development of an Andean-type magmatic arc around ca. 2.5 Ga in the Bastar craton, central India. Highlights • We report detrital zircon U-Pb ages for the intercalated sedimentary units. • We report εHf (t = 2.5 Ga) and εNd (t = 2.5 Ga) in thirty-three bulk-rock basalt samples. • Magmatism and sedimentation were apparently contemporaneous. • Isotopic signatures and geochemical attributes are consistent with an arc setting. • Dongargarh volcano-sedimentary Supergroup represents an Andean-type arc. [ABSTRACT FROM AUTHOR]

Abstract The North Atlantic craton hosts extensive exposures of Eoarchean crust, spread through areas of Western Greenland and Northern Labrador (Canada). Of these two areas, the crust of the Saglek Block of Northern Labrador has received far less attention from the scrutiny of modern analytical methods than its better documented Western Greenland equivalent, the Itsaq Gneiss Complex. Here, we present the first coupled trace element and U–Pb/Hf/O isotope dataset for zircon from an early TTG component of the Saglek Block. The combination of textural, elemental and isotopic in-situ analyses enables selection of the least disturbed zircon domains. From these it is demonstrated that the oldest felsic remnants exposed in the Saglek Block were emplaced 3.86 ± 0.01 billion yr (Ga) ago through partial melting of basaltic protoliths. The Hf isotope signature of the oldest zircon domains from the Saglek Block TTG indicates derivation from sources that did not undergo substantial Lu/Hf fractionation, resulting in initial Hf isotope compositions that are chondritic within uncertainty. The oxygen isotope ratios of the least disturbed zircon portions vary from 5.38 ± 0.16‰ to 6.64 ± 0.19‰ and document the interaction of the TTG protoliths with Earth's early hydrosphere at low temperature (≤150–200 °C) prior partial melting in the Eoarchean. The results support TTG production in the Eoarchean from variably hydrated basaltic protoliths. Highlights • Investigation of the older TTG component of the Saglek Block (Northern Labrador). • New in-situ zircon U–Pb/Hf/O isotope data coupled with trace element analyses. • Chondritic Hf composition of the oldest (ca. 3.86 Gyr) zircon domains. • Zircon δ 18 O VMOW values, up to 6.6 ± 0.2‰, i.e. higher than the typical mantle range. • Low-T hydrothermal alteration of the basaltic protoliths of Eoarchean TTG. [ABSTRACT FROM AUTHOR]

The origin and tectonic evolution of the early Paleozoic arc terranes abutting the northern margin of the North China Craton (NCC) are widely debated. This paper presents detrital zircon U-Pb and Hf isotopic data of early Paleozoic strata in the Zhangjiatun arc terrane of central Jilin Province, northeast (NE) China, and compares them with the Bainaimiao and Jiangyu arc terranes abutting the northern margin of the NCC. Detrital zircons from early Paleozoic strata in three arc terranes exhibit comparable age groupings of 539-430, 1250-577, and 2800-1600 Ma. The Paleoproterozoic to Neoarchean ages and Hf isotopic composition of the detrital zircons imply the existence of the Precambrian fragments beneath the arc terranes. Given the evidences from geology, igneous rocks, and detrital zircons, we proposed that the early Paleozoic arc terranes abutting the northern margin of the NCC are a united arc terrane including the exotic Precambrian fragments, and these fragments shared a common evolutionary history from Neoproterozoic to early-middle Paleozoic. [ABSTRACT FROM AUTHOR]

Hafnium and oxygen isotopic compositions measured in-situ on U-Pb dated zircon from Archaean sedimentary successions belonging to the 2.9–2.8 Ga Belingwean/Bulawayan groups and previously undated Sebakwian Group are used to characterize the crustal evolution of the Zimbabwe Craton prior to 3.0 Ga. Microstructural and compositional criteria were used to minimize effects arising from Pb loss due to metamorphic overprinting and interaction with low-temperature fluids. 207 Pb/ 206 Pb age spectra (concordance >90%) reveal prominent peaks at 3.8, 3.6, 3.5, and 3.35 Ga, corresponding to documented geological events, both globally and within the Zimbabwe Craton. Zircon δ 18 O values from +4 to +10‰ point to both derivation from magmas in equilibrium with mantle oxygen and the incorporation of material that had previously interacted with water in near-surface environments. In ε Hf -time space, 3.8–3.6 Ga grains define an array consistent with reworking of a mafic reservoir ( 176 Lu/ 177 Hf ∼0.015) that separated from chondritic mantle at ∼3.9 Ga. Crustal domains formed after 3.6 Ga depict a more complex evolution, involving contribution from chondritic mantle sources and, to a lesser extent, reworking of pre-existing crust. Protracted remelting was not accompanied by significant mantle depletion prior to 3.35 Ga. This implies that early crust production in the Zimbabwe Craton did not cause complementary enriched and depleted reservoirs that were tapped by later magmas, possibly because the volume of crust extracted and stabilised was too small to influence (asthenospheric) mantle isotopic evolution. Growth of continental crust through pulsed emplacement of juvenile (chondritic mantle-derived) melts, into and onto the existing cratonic nucleus, however, involved formation of complementary depleted subcontinental lithospheric mantle since the early Archaean, indicative of strongly coupled evolutionary histories of both reservoirs, with limited evidence for recycling and lateral accretion of arc-related crustal blocks until 3.35 Ga. [ABSTRACT FROM AUTHOR]

The Archean-Paleoproterozoic high-grade basement of Yudongzi complex is a key to understanding the early Precambrian crustal evolution of the Yangtze craton. It comprises mainly orthogneiss, paragneiss and amphibolite, whose protoliths are tonalitic-trondhjemitic-granitic (TTG), sedimentary and basic-intermediate volcanic rocks, respectively. The TTG gneiss, amphibole plagiogneiss and biotite plagiogneiss yield magmatic zircon LA-ICP-MS U–Pb ages of 2815 ± 18 Ma (MSWD = 0.92), 2692 ± 26 Ma (MSWD = 0.59) and 2449 ± 4 Ma (MSWD = 0.94), respectively. Metamorphic overgrowths on zircon from amphibolite have an age of 1848 ± 5 Ma (MSWD = 0.71). TTG gneisses show medium Sr/Y and variable high (La/Yb) N ratios with low Y and Yb contents. They are characterized by positive Eu anomaly and distinct depletion of HREE together with negative Nb, Ta and Ti, implying amphibole, garnet and minor rutile as residual phases. Their positive ε Hf (t) values of +2.1 to +8.1 with T DM2 of ca. 2.80–3.10 Ga suggest significant reworking of juvenile crust. Amphibole plagiogneisses display a strong enrichment of LREEs and depletion of Nb, Ta and Ti. Additionally, a relative enrichment of Ba, Rb, Pb and Zr, as well as high Cr and Ni contents and Mg # values, imply a mantle source with the addition of continental crust material. Zircon ε Hf (t) values vary between −0.9 and +3.9, suggesting a proportionally significant input of juvenile material and therefore interaction between the mantle and pre-existing continental crust. Biotite plagiogneisses show negative ε Hf (t) values between −3.4 and −0.1 with a few positive ε Hf (t) values ranging from +0.1 to +1.5. Together with T DM2 ages of ca. 2.80–3.00 Ga, these ε Hf (t) values suggest that these rocks were mainly generated by reworking of ancient crust. Thus, the Yudongzi complex exposed in the northern part of the Yangtze craton has experienced significant reworking of juvenile crust at ca. 2.80 Ga and subsequent crustal growth at ca. 2.70 Ga, followed by a second stage of reworking of ancient crust at ca. 2.45 Ga. During the Late Paleoproterozoic, the Yudongzi complex was probably involved in the amalgamation of the Paleoproterozoic supercontinent Columbia, and affected by a post-collisional metamorphic event at ca.1.85 Ga. [ABSTRACT FROM AUTHOR]

A study of U-Pb and Lu-Hf-Yb isotope data in zircons from metamorphosed psammopelite and quartzite from the type area of Archaean Sargur Group, Dharwar Craton, India is carried out. Two age populations are observed: an older population with concordant U-Pb ages between 2.7 and 2.8 Ga, and a younger population with ages in the 2.4-2.6 Ga age range. The εHf values of 0 to +2.0 for the older zircon population suggest that they were derived from juvenile crust formed at 2.7-2.8 Ga. Sub-chondritic εHf values for the younger population indicate metamorphism and/or crustal reworking at ~2.5 Ga. Metasedimentary enclaves in the Sargur type area are therefore part of the gneiss-supracrustal complex of different antiquities and may not have an independent stratigraphic status. [ABSTRACT FROM AUTHOR]

The Qin-Fang Trough, South China, trends northeast-southwest, orthogonal to the adjoining southern margin of the craton. The Devonian strata within the trough are unconformable on late Neoproterozoic units of the Yunkai Massif, indicating that strata within the trough are autochthonous. U-Pb ages and Hf isotope compositions of detrital zircons from the Silurian to Devonian succession are consistent with derivation from the massif. In comparisons of our data with those fromequivalent units in the Ailaoshan Belt andHainan Island, detrital zircons fromthe Silurian strata show similar age distributions andHf isotope compositions, indicating that the three areas shared a common source andwere adjacent to each other during the Silurian. In contrast, the age distributions of detrital zircons preserved in Devonian strata in the Qin-Fang area are different from those of equivalent units in the Ailaoshan Belt. This, along with the absence of Devonian strata on Hainan Island, suggests that the Qin-Fang area had separated fromthe Ailaoshan Belt by the Devonian. This change is linked to opening of the Ailaoshan Ocean, which was synchronous with expansion of the Qin-Fang Trough and the adjoining Youjiang Basin into epicontinental basins during the Devonian and Carboniferous. Combining these findings with temporal and spatial correlations, we conclude that the Qin-Fang Trough originated as an aulacogen: a "failed" rift of a three-armed rift system, with the other two rift arms evolving into the AilaoshanOcean during the opening of Paleo-Tethys. The Ailaoshan Ocean was an Atlantic-type oceanic basin with rifting commencing in the Early Silurian. [ABSTRACT FROM AUTHOR]

The Miyun area of Beijing is located in the northern part of the North China Craton (NCC) and includes a variety of Archean granitoids and metamorphic rocks. Magmatic domains in zircon from a tonalite reveal Early Neoarchean (2752±7 Ma) ages show a small range in ∊Hf( t) from 3.1 to 7.4 and tDM1(Hf) from 2742 to 2823 Ma, similar to their U-Pb ages, indicating derivation from a depleted mantle source only a short time prior to crystallization. SHRIMP zircon ages of granite, gneiss, amphibolite and hornblendite in the Miyun area reveal restricted emplacement ages from 2594 to 2496 Ma. They also record metamorphic events at ca. 2.50 Ga, 2.44 Ga and 1.82 Ga, showing a similar evolutionary history to the widely distributed Late Neoarchean rocks in the NCC. Positive ∊Hf( t) values of 1.5 to 5.9, with model ages younger than 3.0 Ga for magmatic zircon domains from these Late Neoarchean intrusive rocks indicate that they are predominantly derived from juvenile crustal sources and suggest that significant crustal growth occurred in the northern NCC during the Neoarchean. Late Paleoproterozoic metamorphism developed widely in the NCC, not only in the Trans-North China Orogen, but also in areas of Eastern and Western Blocks, which suggest that the late Paleoproterozoic was the assembly of different micro-continents, which resulted in the final consolidation to form the NCC, and related to the development of the Paleo-Mesoproterozoic Columbia or Nuna supercontinent. [ABSTRACT FROM AUTHOR]

Combined whole-rock, U–Pb zircon and monazite dating, in situ zircon (MC)-SF-ICP-MS Lu–Hf-isotope data are reported for more than 20 Archaean granitoid samples to constrain magmatic events and their sources in the Bundelkhand Craton, northern India. The results are crucial for understanding the extent of reworking vs juvenile crustal growth during Palaeoarchaean–Neoarchaean and also provide new information on the temporal gap between Palaeoarchaean TTG and Neoarchaean granodiorite–granite magmatism. These data reveal that the Bundelkhand Craton was affected by at least four discrete episodes of Palaeoarchaean TTG magmatism between 3.55 Ga and 3.20 Ga at regular intervals of 100–150 Myr. After a period of about 500 Myr of near magmatic shutdown, it was followed by a relatively short-lived, but more voluminous granitoid emplacement event during the Neoarchaean at 2.58–2.50 Ga, during which minor granodioritic gneisses and voluminous granites intruded. The new data also provide evidence for a metamorphic overprint at ca. 3.20 Ga, and a Pan-African tectonothermal overprint at 0.50–0.60 Ga. Hf-isotope and whole-rock geochemical data of the TTGs suggest a complex process of crust formation and stabilisation during the Palaeoarchaean, mainly by the reworking of older mafic and felsic crust between 3.55 and 3.20 Ga. The CHUR parallel array for the TTGs may indicate that these rocks were formed by partial melting of an oceanic crust that was derived from chondritic mantle sources, shortly before formation of TTG. This interpretation is inconsistent with Hf-isotope data from worldwide sources, which provide evidence for a successive mantle depletion since at least 4.0 Ga, resulting in εHf t of about +5.0 at 3.0 Ga. Intense melting of the heterogeneous TTG crust during the Neoarchaean resulted in the coeval formation of granodioritic gneisses and voluminous granites, and subordinate hybrid granites with a minor contribution of melts from an enriched mantle source, affected by subduction-zone processes prior to 2.55 Ga. [ABSTRACT FROM AUTHOR]

The Adrar Souttouf Massif is located at the western margin of the West African Craton and consists of several NNE–SSW trending units. Of them, the two westernmost have been interpreted to be linked with the Avalonian terrane assemblage and Meguma, respectively. New Hf isotopic data corroborates the Avalon correlation but has no impact one way or another on the possible Meguma connection, as there is no Hf data available from the latter. The obtained pattern of εHf (t) values vs. zircon age of the likely Avalonia related Oued Togba unit is similar to published data from Avalonia. Zircons of this unit show characteristic patterns of crustal mixing at 0.7 to 1.3 Ga and 1.75 to 2.25 Ga, while juvenile crust was likely formed around 0.6 to 0.75 Ga, from 1.2 to 2.2 Ga, and between 2.5 and 3.2 Ga. The zircons of the Sebkha Gezmayet unit reveal crustal mixing for the entire Palaeozoic and Neoproterozoic, from 2.05 to 2.11 Ga, and 2.8 to 2.9 Ga. Juvenile crust formation is interpreted to have occurred from 0.5 to 0.7 Ga, at around 2.1 Ga, and at ca. 2.9 Ga. As Mesoproterozoic zircons are abundant in the likely Avalonia-like Oued Togba unit, but uncommon at the West African Craton, their origin has to be found elsewhere. A comparison of available Hf data from Amazonia and Baltica, the two potential source cratons of Avalonia, shows similarities but is hampered by the lack of available data from Amazonia. Finally, a few grains from both units have Eoarchaean model ages. Among similar grains from other peri-Gondwanan terranes, they give indication of partial recycling of Eoarchaean crust in the vicinity of the northwestern West African Craton. [ABSTRACT FROM AUTHOR]

The Northern Liaoning Complex in northeastern China constitutes an important component of the Eastern Block in the North China Craton. The major lithologies consist of Archean granitoid gneisses with minor supracrustal rocks occurring as tectonic lenses. This study presents zircon Lu–Hf isotopic data for the first time as well as new SHRIMP zircon U–Pb data of the major lithologies from the Northern Liaoning Complex, in order to elucidate the crustal evolution of the complex and provide new constraints on the Neoarchean crustal evolution of the Eastern Block in the North China Craton. Magmatic zircon U–Pb data from this study show that the protolith magmas of the supracrustal rocks and granitoid gneisses were generated during ∼2.55–2.50 Ga. Metamorphic zircons document consistent metamorphic ages at 2.49–2.48 Ga, suggesting a regional metamorphic event immediately after the magmatism at the end of the Neoarchean in the Northern Liaoning Complex. Inherited/detrital zircons of 2.79–2.60 Ga suggest possible existence of ancient crust in this region. Zircon Lu–Hf isotopic compositions show that the magmatic zircons have variable ɛ Hf ( t ) values from −4.0 to +9.0 with depleted mantle model ages of 3.6–2.5 Ga, of which most ɛ Hf ( t ) values are positive with a model age peak at 2.9–2.7 Ga. These zircon Hf signatures reveal major juvenile crustal growth with additions of older crustal materials during 2.9–2.7 Ga, and a crustal reworking event with minor juvenile additions at 2.6–2.5 Ga in the studied area. Integrated with previous data from other Neoarchean complexes in the Eastern Block, both the major juvenile crustal growth during 2.9–2.7 Ga and the strong crustal reworking at 2.6–2.5 Ga contribute to the extensive Neoarchean crust formation of the Eastern Block in the North China Craton. The North China Craton share similar Neoarchean continental crustal evolution to other cratons in the world, though it is distinctively featured by intensive tectonothermal overprinting at the end of the Neoarchean. [ABSTRACT FROM AUTHOR]

The results of simultaneous LA-ICP-MS measurements of 207 Pb/ 206 Pb and Hf isotope ratios are reported for zircons separated from five Ukrainian shield sedimentary rocks: (1) c. 3.0 Ga quartzite of the Bug Series; (2) c. 2.0 Ga quartzite of the Topilnya Series; (3) c. 1.75 Ga quartzite of the Ovruch Series; (4) c. 1.2–1.0 Ga sandstone of the Polissya Series; and (5) c. 0.6 Ga conglomerate of the Volyn Series. The age–Hf isotope (ɛHf T ) data indicate four main crustal growth events at 3.75, 3.20–3.15, 2.2–2.0, and 1.5 Ga in the south-western part of the East European craton (EEC). An additional rather minor event could have place at 2.5–2.4 Ga. The oldest event is represented by enderbites of the Bug domain in the south-western part of the Ukrainian shield. The second crust-forming event occurred at c. 3.20–3.15 Ga and it is documented by detrital zircons separated from the Bug Series quartzite and metasediments of the Soroki greenstone belt, Azov domain. A small number of zircons with positive ɛHf T values reveal some input of the juvenile material into the crust at 2.5–2.4 Ga, whereas the 2.2–2.0 Ga event is dominated by zircons with positive ɛHf T values. The youngest event is represented by numerous zircons that crystallized at c. 1.5 Ga. The possible sources of these zircons are the rock complexes of the south-western part of the Fennoscandian shield. [ABSTRACT FROM AUTHOR]

Charnockites (pyroxene-bearing granitoids) of magmatic origin in diverse tectonic settings and ranging in age from Mesoarchean to Cretaceous constitute important components of the continental crust. Here we report charnockites displaying both magnesian and ferroan compositions associated with gabbros from an AMCG (anorthosite–mangerite–charnockite–granite) suite in the North China Craton. The orthopyroxene in the magnesian charnockite is characterized by moderate X Mg of 0.63–0.65 (Wo 1–2 En 62–63 Fs 35–36 ), and low Al 2 O 3 content of 0.59–0.71 wt.%. The magnesian charnockites show medium- to high-K contents, and high Mg# (~ 47–69) similar to that of gabbros, whereas the Mg# of the ferroan charnockites is low (~ 6–28). The ferroan charnockites are alkali-calcic to alkalic, and weakly peralkaline to metaluminous, whereas the magnesian charnockites are calcic to calc-alkalic, and metaluminous. Although magnesian charnockites are in general considered to have formed in subduction setting, the medium- to high-K contents, high Mg# values with a wide range, and the highly negative εHf values of the zircons in these rocks (− 8. 4 to − 13.6), suggest inheritance of the arc signature from the melting of ancient arc-related crustal material. The ferroan charnockites show tholeiitic affinity and define a common differentiation trend with the gabbroic anorthosites and likely represent fractionated end-members with or without crustal interaction in a post-collisional rift setting. We present U–Pb age data from zircon grains on seven samples including two ferroan charnockites, three magnesian charnockites, one gabbroic enclave in magnesian charnockite and one gabbroic anorthosite which show emplacement ages of 1748.8 ± 6.4 Ma, 1747.1 ± 9.5 Ma, 1756.4 ± 7.3 Ma, 1756.7 ± 9.2 Ma, 1731 ± 17 Ma, 1731.6 ± 8.2 Ma and 1746.5 ± 7.3 Ma respectively. The negative εHf values (− 1.2 to − 13.6) of zircon grains from these rocks and the older crustal model ages ranging from Mesoarchean to Paleoproterozoic suggest that the magma sources of these rocks involved the melting of ancient crustal components. The age data suggest that the magmatic suite was emplaced within a relatively short time interval between1.73 and 1.76 Ga, during late Paleoproterozoic, placing the rocks suite in a post-collisional scenario, following the amalgamation between the Eastern and Western Blocks of the North China Craton along the Trans-North China Orogen at ca. 1.85–1.80 Ga. [ABSTRACT FROM AUTHOR]

The northern margin of the Tarim Craton plays a pivotal role in understanding the crustal evolution and supercontinent reconstruction of the Tarim Craton. Here we integrate LA-ICP-MS U–Pb ages and Hf isotopic data for detrital zircons from Neoproterozoic successions in the Aksu area, NW Tarim. A total of 679 concordant U–Pb ages define four age populations of 2600–2200 Ma, 2050–1800 Ma, 950–700 Ma and 680–600 Ma, which are consistent with the episodes of magmatism and metamorphism documented in the northern Tarim Craton, suggesting that the detritus were likely sourced from the northern Tarim Craton itself. The oldest age population corresponds to the Neoarchean to early Paleoproterozoic magmatic event related to an important stage in the development of the proto continental crust in the Tarim Craton. The 2050–1800 Ma age population represents a magmatic–metamorphic event during a middle Paleoproterozoic orogeny, possibly related to the assembly of Tarim to the Columbia supercontinent. The dominant Neoproterozoic detrital zircons display a major cluster between 950 Ma and 700 Ma (peak at ca. 850 Ma), much younger than the typical Grenvillian ages. This is similar to detrital zircon data sets from Yangzte and northern India, implying that these blocks shared a similar evolution pattern in the Rodinia supercontinent. The early Pan-African (680–600 Ma) ages are comparable with those reported from the Arabian-Nubian Shield, but quite different from those from other Gondwana blocks, implying a possible correlation of Tarim with the Eastern Africa Orogen. Abundant zircons yield Archean (3.9–2.5 Ga) Hf model ages (T DM C ), suggesting the presence of extensive Archean basement as old as Paleoarchean in the Tarim Craton. Some Neoarchean and Neoproterozoic zircons have high positive ɛ Hf ( t ) values, indicating significant juvenile addition from the depleted mantle at those periods. However, most detrital zircons show negative ɛ Hf ( t ) values, suggesting that crustal reworking was the dominant process in the generation of the episodes of magmatism in the Tarim Craton. At last, based on the stratigraphic settings and the comparison of detrital zircon data, the Aksu Group and the Qiaoenbrak Formation are most likely units with equivalent depositional age. [ABSTRACT FROM AUTHOR]

The Yangtze Craton is one of the most important cratonic blocks in eastern Asia. However, its early evolution has not been well constrained yet, because of the poor exposure of Archean basement rocks. In this contribution, a combined study of zircon U–Pb age, Hf–O isotope compositions, as well as whole rock element compositions was carried out for gray gneiss rocks from the Douling complex in the northwestern part of the Yangtze Craton. Zircon U–Pb dating for two gneiss samples yielded weighted mean ages of 2509 ± 21 and 2496 ± 15 Ma. The gray gneisses have high SiO 2 (63.64–73.74%), Na 2 O (3.66–6.21%), but low K 2 O (0.76–2.93%) contents, and belong to the trondhjemite, tonalite and granodiorite series rocks. They are characterized by enrichments of LILEs and LREEs, but notable depletions in Nb–Ta and Ti, as well as heavy REEs and Y. All the samples plot into the fields of typical Archean TTG rocks in the (La/Yb) N vs. (Yb) N and Sr/Y vs. Y diagrams. Therefore, the gray gneisses in the Douling complex are Neoarchean TTG rocks. The relatively high Nb/Ta and Zr/Sm ratios of 19.6–46.0 and 14.5–143.4 suggest their formation under eclogite-facies conditions. They have low ɛ Hf ( t ) values of −3.21 and −3.39 and Hf model ages of 3194 ± 26 and 3205 ± 24 Ma, indicating their derivation from ca. 3.2 Ga juvenile mafic rocks. Their δ 18 O values of 6.41 ± 0.12 and 5.44 ± 0.12‰ suggest that surface rocks were differently recycled into their sources. Collectively, the TTG rocks in the Douling complex were generated by partial melting of thickened mafic crust rather than direct partial melting of oceanic crust in a convergent plate boundary. A compilation of available zircon U–Pb and Hf isotope compositions of the Yangtze Craton reveals that there are quite differences of Hf isotope compositions in Archean. The ca. 3.8–3.4 Ga zircons exhibit ɛ Hf ( t ) values of −5.8 to 0.0. These chondritic to slightly enriched hafnium isotope compositions imply that their host rocks were formed by protracted intra-crustal reworking of ancient protoliths without juvenile input. By contrast, zircons with ages younger than ca. 3.2 Ga register both negative and positive ɛ Hf ( t ) values up to the depleted mantle, providing clear evidence for the addition of juvenile materials. These imply that the subduction-driven plate tectonics might have been operated since ca. 3.2 Ga in the Yangtze Craton. [ABSTRACT FROM AUTHOR]

Supracrustal successions in the Zhaertai–Bayan Obo–Huade rift zone on the northern margin of the North China Craton include the Zhaertai, Bayan Obo and Huade Groups from west to east. The Huade Group, which has been subdivided into four formations, is composed of basal pebbled quartzites, quartzites, schists, phyllites, marbles, slates and diopsidites. Geochemistry of the metasedimentary succession indicates that source rocks of the lower two formations are felsic, displaying passive margin signatures, whereas those of the upper two formations have continental island arc or active continental margin signatures. U–Pb ages of detrital zircons from the group yielded three age populations of 2690–2450, 2150–1710 and 1660–1330 Ma, of which the youngest age population only exist in the upper Huade Group. The dominant 2690–2450 detrital zircons were likely sourced from the granitic rocks in the Yinshan Block. The subordinate 2150–1710 Ma detrital zircons were probably recycled from the metasedimentary units from the Khondalite Belt and/or derived from the similar aged granitic plutons of the Hongqiyingzi “Group”, which are also evidenced by the similar geochemical features of rutiles from the Huade Group and the Khondalite Belt. Minor amounts of 1660–1330 Ma detrital zircons may have derived from the North American and/or Baltica cratons connected to the northern margin of the North China Craton in the Columbia supercontinent. The youngest detrital zircon age peak of ∼1337 Ma in the upper Huade Group suggests that the sedimentation began after ∼1.34 Ga. In combination with the ∼1320 Ma granitoids cross-cutting it, depositional ages of the upper Huade Group can be constrained between ∼1.34 and ∼1.32 Ga. Taking into account the lithostratigraphic features, provenances and depositional ages, a continental rift basin deposit represented by the upper Huade Group on the northern margin of the North China Craton developed between ∼1.34 and ∼1.32 Ga, which indicates that the final breakup of the North China Craton from the Columbia supercontinent happened in the middle Mesoproterozoic. [ABSTRACT FROM AUTHOR]

The Precambrian evolution of the Tarim Craton in NE China, in particular during the early Precambrian stage, remains enigmatic. In this contribution, we report field observation, petrology, geochemistry, zircon Lu–Hf isotopes and U–Pb ages of the major rock formations of the Aketage area in the southeastern section of the Tarim Craton. The Milan Group in Aketage is dominantly composed of 2.7–2.5 Ga gneissic amphibolite–TTG complex with minor paragneiss. Both the mafic and silicic rocks exhibit geochemical features consistent with an arc affinity. The arc-signature of the 2.01–2.03 Ga gneissic granites and gabbros which intrude the Archean basement, as well as the major 2.0 Ga metamorphic event revealed by zircon U–Pb dating, suggest an important subduction-collision event possibly related to the assembly of the Paleoproterozoic Columbia supercontinent. The ca. 1848–1856 Ma massive potassic granites, 1867 Ma mafic dyke swarm and 1844 Ma massive leucogranite dykes reveal magmatism in a post-collisional extensional setting. A comprehensive synthesis of the major orogenic events and continental crust growth process from the different Precambrian terranes in Tarim Craton show significant discrepancy in time related to the late Neoarchean crust formation ages and the Paleoproterozoic orogenic events. For example, the major orogenic event took place at ∼1.85 Ga in Quruqtagh-Dunhuang terrane, at ∼1.90 Ga in the southwest Tarim Craton and at ∼2.0 Ga in the Aketage-Qaidam terrane. These different terranes exhibit distinct periods of continental crust growth in the early Precambrian. Continental growth in the Aketage area took place during 2.7–4.3 Ga. The 3.6 Ga xenocrystic zircons as well as the peak of 4.2 Ga zircon Hf model ages, indicate the possible existence of Paleoarchean and even Hadean crust in the Aketage area. In the Quruqtagh-Dunhuang terrane, the growth of early Precambrian continental crust took place at 2.6–3.3 Ga with peaks at ca. 2.6–2.7 Ga and 3.0 Ga. The diachronous late Paleoproterozoic orogenic events and the significant difference in continental growth process suggest that the Precambrian basement of the Tarim Craton is composed by independent continental terranes possibly detached from the cores of discrete ancient cratonic nuclei, which were not unified until the early Neoproterozoic during assembly of the Rodinia supercontinent. [ABSTRACT FROM AUTHOR]

Highlights: [•] Regression of detrital zircon Hf-age data yield consistent 176Lu/177Hf values (0.01). [•] Detrital zircon Hf–O isotopes imply dominant crustal reworking during 2.0–3.5Ga. [•] The oldest continental crust in the northern Tarim Craton was formed before 3.9Ga. [•] Intracrustal differentiation occurred as early as 3.5Ga during the Paleoarchean. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Salem Block forms part of the lower crust of the Eastern Dharwar Craton. [•] Peak metamorphism in the Salem Block was dated as ∼2.53Ga. [•] Shear zones hold deepest exposures of Eastern Dharwar roots (∼2.75–2.65Ga). [•] Cryogenian and Ediacaran intrusions formed during consumption of Mozambique Ocean. [ABSTRACT FROM AUTHOR]

The collision between the North and South China cratons in Middle Triassic time (240-225 Ma) created the world's largest belt of ultrahigh-pressure (UHP) metamorphism. U-Pb ages, Hf isotope systematics and trace element compositions of zircons from the Xugou, Yangkou and Hujialing peridotites in the Sulu UHP terrane mainly record a ~470 Ma tectonothermal event, coeval with the Early Paleozoic kimberlite eruptions within the North China craton. This event is interpreted as the result of metasomatism by fluids/melts derived from multiple sources including a subducting continental slab. The peridotites also contain zircons with ages of ~3.1 Ga, and Hf isotope data imply a component ≥3.2 Ga old. Most zircon Hf depleted mantle model ages are ~1.3 Ga, suggesting that the deep subcontinental lithospheric mantle beneath the southeastern margin of the North China craton experienced a intense mid-Mesoproterozoic metasomatism by asthenospheric components, similar to the case for the eastern part of this craton. Integrating data from peridotites along the southern margin of the craton, we argue that the deep lithosphere of the cratonic margin (≥3.2 Ga old), from which the Xugou, Yangkou and Hujialing peridotites were derived, experienced Proterozoic metasomatic modification, followed by a strong Early Paleozoic (~470 Ma) tectonothermal event and the Early Mesozoic (~230 Ma) collision and northward subduction of the Yangtze craton. The Phanerozoic decratonization of the eastern North China craton, especially along its southern margin, was not earlier than the Triassic continental collision. This work also demonstrates that although zircons are rare in peridotitic rocks, they can be used to unravel the history of specific lithospheric domains and thus contribute to our understanding of the evolution of continental cratons and their margins. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Kuluketage and Dunhuang Blocks have a uniform Precambrian basement within the Tarim Craton. [•] An important episode of crustal growth at ∼2.0Ga occurred in the Tarim Craton. [•] The ∼1.85Ga magmatic event in the Tarim Craton was related to the assembly of the Columbia supercontinent. [•] The ∼1.75Ga magmatism was formed in a post-collisional tectonic setting. [Copyright &y& Elsevier]

Highlights: [•] Two new paragneisses containing detrital zircons as old as 3.8Ga were reported. [•] Multi-phased crustal addition and recycling from 3.8 to 3.4Ga were identified. [•] A nearly complete Archean crustal evolution was recorded in eastern Hebei. [Copyright &y& Elsevier]

Abstract: Most layered mafic intrusions (LMI) are formed via multiple magma injections into crustal magma chambers. These magmas are originally sourced from the mantle, likely via plume activity, but may interact with the overriding lithosphere during ascent and emplacement in the crust. The magma injections lead to the establishment of different layers and zones with complex macroscopic, microscopic and cryptic compositional layering through magmatic differentiation and associated cumulate formation, sometimes accompanied by crustal assimilation. These complex mineralogical and petrological processes obscure the nature of the mantle sources of LMI, and typically have limited the degree to which parental liquids can be fully characterised. Here, we present Lu–Hf isotope data for samples from distinct layers of the Upper Zone of the Windimurra Igneous Complex (WIC), an immense late-Archean LMI in the West Australian Yilgarn Craton. Lu–Hf isotope systematics of whole rocks are well correlated ( , ) with an age of Ga and initial . This age, however, is older than whole rock Sm–Nd and zircon U–Pb ages of the intrusion, both of which are ca. 2.8 Ga. Stratigraphically-controlled initial Hf isotope variations (associated with multiple episodes of emplacement at ca. 2.8 Ga) indicate isotope mixing between a near-chondritic and an ultra-radiogenic component, the latter with . This Hf isotope mixing creates a pseudochron-relationship at the time of intrusion of ∼250 Myr that is superimposed on subsequent radiogenic ingrowth after crystallisation, generating an age that predates the actual emplacement event. Mixing between late-stage crystallisation products (melt + crystals) from the Middle Zone and replenishing, plume-derived liquids was followed by crystal accumulation in a chemically evolving magma chamber. The ultra-radiogenic Hf isotope endmember in the WIC mantle source requires parent–daughter ratios consistent with very early formation in Earth history, akin to early Archean komatiitic plume sources. We propose that plume-derived melts that formed the Windimurra LMI reacted with ancient refractory lithospheric keels already underpinning ancient cratons, creating a melt with extremely high . Melting a refractory component with super-chondritic, time-integrated high Lu/Hf, in this case by plume–lithosphere interaction, simultaneously accounts for the extreme Hf isotope signals, Hf–Nd isotope decoupling, and difference in radiometric Lu–Hf and Sm–Nd ages. [Copyright &y& Elsevier]

Abstract: SHRIMP zircon U–Pb dating of the Huangjinshan granite porphyry in the Wutai area, North China Craton (NCC) yielded concordant ages, with a weighted mean 207Pb/206Pb age of 2137±9Ma, which indicates that the granite was emplaced in the middle Paleoproterozoic. The granite porphyry is enriched in SiO2, REEs (except Eu), Zr, Nb, Ga, Y and Zn, and depleted in MgO, CaO, Al2O3, Sr, Ba, V, Cr and Ni, with high FeO*/MgO ratios. With the zircon saturation temperatures ranging from 856 to 895°C and a lack on detected inherited zircon, this indicates it is a ‘hot’ A-type granite, of the type emplaced in anorogenic or extensional settings with high heat flow. Zircons in the granite porphyry have ε Hf(t) values ranging from −1.72 to +1.84, and Hf model T DM1 ages of 2429–2554Ma. The Hf isotopes indicate source of the granites was pre-Neoarchean continental crust mixed with mafic rocks derived from depleted mantle, or directly from the partial melting of ca. 2.5Ga crust. Given that there are no syn-plutonic gabbro enclaves in the Huangjinshan granite porphyry, it is preferred that it originated mainly from partial melting of ca. 2.5Ga upper crust without mixing with mantle-derived magma. 2.2–2.0Ga volcanic and plutonic rocks, which exhibit bimodal magma characteristics emplacing in rifting setting, are abundant in the central NCC. The results presented here are further evidence for that 2.2–2.0Ga is an important stage of Paleoproterozoic rifting in the central NCC. [Copyright &y& Elsevier]

Abstract: The Dunhuang block, in the easternmost segment of the Tarim craton, exposes Precambrian mafic granulite and felsic gneiss. To better understand the poorly known formation and evolution of the Tarim craton, we carried out detailed field-based petrological and geochronological investigations on the major lithologies of the Dunhuang block. U–Pb dating and Hf isotopic analyses on the mafic granulite and felsic gneiss (TTG gneiss) of the Dunhuang block reveal two distinct age populations: the Latest Neoarchaean (∼2.5Ga) and the Late Palaeoproterozoic (1.82–1.85Ga). The zircon magmatic cores and metamorphic rims of tonalitic gneisses yield similar ages of ∼2.5Ga, supporting the existence of Archean rocks in the Dunhuang block. The short time interval between Latest Neoarchean magmatism and high-grade metamorphism suggests that they were related to the same Latest Neoarchean tectonothermal event. The ∼2.5Ga zircons show Hf-depleted mantle model ages between 2.55Ga and 2.8Ga with a peak at ∼2.7Ga, suggesting that ∼2.7Ga juvenile crust of the Dunhuang block was reworked during a 200–300m.y. period at the end of the Neoarchean. The age of ∼1.85Ga obtained from the mafic granulites and felsic gneisses is interpreted as the age of high-pressure granulite facies metamorphism. Combined with the Hf isotopic data, these data suggest that the Dunhuang block experienced ∼2.7Ga crustal growth, a ∼2.5Ga magmatic–metamorphic event and a 1.82–1.85Ga (HP) granulite facies metamorphic event. This sequence of events is very similar to that of the North China Craton, implying that the evolutionary history of the Dunhuang block was consistent with that of the North China Craton from the Neoarchean to Paleoproterozoic. [Copyright &y& Elsevier]

Highlights: [•] Permian to Triassic zircon ages from magmatic suite. [•] Hf isotopes and Nd isotopes indicate contribution from both mantle and crust. [•] Multiple pulses of magma with fractionation, hybridization and assimilation. [•] Time-integrated εHf(t) values indicate progressive mantle upwelling. [ABSTRACT FROM AUTHOR]

Abstract: The Jianping gneissic terrane (JPGT), Western Liaoning Province (WLP) at the northwestern margin of the Eastern Block of the North China Craton is one of the major Neoarchean high-grade metamorphic terranes. The region is composed dominantly of metamorphosed volcanic and pyroclastic rocks and granitoid gneisses. Geological and petrological features together with geochemical data suggest that the magmatic precursors of these granitoid gneisses are tonalite, trondhjemite, granodiorite (TTG), diorite and monzogranite. Whereas the TTGs show strong gneissic fabric, the monzogranitic rocks are only weakly gneissic and generally display massive structures. LA-ICPMS zircon U–Pb isotopic analyses reveal that the dioritic and TTG gneisses formed at 2506–2532Ma, followed by the emplacement of the monzogranitic gneisses at ∼2496Ma. These granitoid gneisses can be classified into two groups: a low silica group (LSG) and a high silica group (HSG). Detailed petrogenetic studies suggest that the dioritic gneisses (LSG) were derived from the partial melting of an enriched mantle source metasomatized by slab fluids, whereas the tonalitic and granodioritic gneisses of the LSG were produced by the partial melting of subducted oceanic slabs and the melts were contaminated by mantle peridotites during their ascent. In comparison, the HSG granitoid gneisses were generated by the partial melting of the lower continental crust composed mainly of metamorphosed basaltic (garnet amphibolites) and pelitic rocks. Comprehensive zircon U–Pb dating and Lu–Hf isotopic data indicate that the JPGT and the North Chaoyang-Fuxin-Yixian granite-greenstone belt (NCFY-GGB) experienced nearly the same crustal evolution during Neoarchean to early Paleoproterozoic time and major crustal growth at ∼2.5 and ∼2.7Ga was recorded in the WLP. Collectively, the WLP preserves a complex geodynamic history from the mid-ocean ridge, through intra-oceanic arc to Andean-type active continental margin. [Copyright &y& Elsevier]

The Gantaohe Group is an important early Precambrian unit in the Trans-North China Orogen, North China Craton, and is mainly composed of greenschist-facies metabasalt, meta-sandstone and dolomitic marble. We report whole-rock geochemical compositions and SHRIMP zircon ages as well as LA-ICP-MS Hf-in-zircon isotopeic analyses for metabasalts from the Gantaohe Group. SHRIMP dating yielded a weighted mean Pb/Pb age of 2087±16 Ma (MSWD=1.3) for magmatic zircons, but there are also abundant ca. 2.5 Ga inherited zircon xenocrysts. The magmatic zircons shows a large ɛ( t) variation in ɛ( t) from −7.17 to +0.45, suggesting an isotopically highly heterogeneous source for the metabasalt. Chemically all samples show no distinct Zr or Hf anomalies, and some samples show no Nd or Ta anomalies in a primitive mantle-normalized trace element variation diagram, and their whole-rock ɛ( t) values range from 4.0 to −0.8. We suggest that the basalt is formed by partial melting of a depleted mantle source, followed by significant crustal contamination. Field observations, the presence of abundant inherited zircon, as well as isotope and trace elements geochemistry support formation of the Gantaohe Group on top of a continental basement. These data and the regional geology lead us to conclude that the Trans-North China Orogen constituted an intracontinental rift during the Paleoproterozoic that was connected to the Eastern Block since the end of the Archean. [ABSTRACT FROM AUTHOR]

Abstract: Large volumes of diabase sills occur within the late Paleoproterozoic to Mesoproterozoic sedimentary rocks in the northern part of the North China Craton (NCC) and previous geochronological studies suggest some of these were emplaced in the Mid-Mesoproterozoic (Ectasian). Here we present new zircon and baddeleyite SHRIMP, LA-ICP-MS and SIMS U–Pb analyses on representative samples of the diabase sills emplaced into the Wumishan, Tieling and Xiamaling Formations. The results show emplacement ages ranging from 1325±5Ma to 1316±37Ma, suggesting voluminous magmatism leading to the formation of the diabase sill swarms (the Yanliao mafic sill swarms) in the Mid-Mesoproterozoic. Zircon LA-ICP-MS U–Pb dating of the Shangdu-Huade granitic pluton in the northern NCC yielded similar emplacement ages ranging from 1331±11Ma to 1313±17Ma. These ages are comparable with the 1.4–1.2Ga rift-related anorogenic magmatism recorded elsewhere on the globe such as North America, Greenland, Baltica, and Siberia, associated with the breakup of the Columbia (Nuna) supercontinent. The Mid-Mesoproterozoic magmatic rocks in the northern NCC constitute a typical bimodal magmatic suite. The geochemical and Nd–Hf isotopic data suggest that the diabasic rocks were likely generated by partial melting of the depleted asthenosphere mantle coupled with slight crustal assimilation in a continental rift setting; however, the granitic rocks were generated mainly through partial melting of the ancient continental crust, probably induced by the upwelling of hot asthenosphere mantle during continent rifting processes. The recognition of these bimodal magmatic rocks indicates that the northern NCC experienced Mid-Mesoproterozoic rifting events that are considered to have led to the final breakup of the Columbia supercontinent. The breakup of the NCC from the Columbia supercontinent occurred during Mid-Mesoproterozoic time, probably at around 1.33Ga. The carbonatite rocks and rare earth element-niobium mineralization in the giant Bayan Obo ore deposit in the northern NCC were also probably related to the continental rifting event in the Mid-Mesoproterozoic. [Copyright &y& Elsevier]

Abstract: A comprehensive review of U–Pb geochronology and Hf isotopes of zircons separated from granulite xenoliths entrained in Phanerozoic magmatic rocks and inherited xenocrysts from the associated lower crust rocks from various domains of the North China Craton (NCC) provides new insights into understanding the evolution of the lower crust in this part of the Precambrian nucleus of Asia. The oldest zircons recorded in granulite xenoliths show ages up to 3.6Ga, slightly younger than the oldest zircons (3.8Ga) from samples of the exposed Archean upper crust. However, the Hf isotope features indicate that the oldest lower crust might have been derived from a 4.0 to 4.1Ga primordial crust as indicated by the data from an inherited zircon in the North Qinling Orogenic Belt at the southern part of the NCC. Our synthesis also suggests that ca. 2.5Ga mark an important period for the evolution of the lower crust of the NCC and the cratonization of the Archean blocks in the NCC, at least for the Eastern Block, with a possible link to mantle plume activity. The occasional presence of zircons with 2.6–3.1Ga ages in the lower crustal granulite xenoliths suggests a continuous reworking of the Paleoarchean lower crust during the Archean. The comprehensive data also show that 1.8–2.0Ga period was the first significant event for the evolution of the lower crust after the cratonization of the Archean blocks of the NCC, which affected the whole lower crust of the Eastern NCC. Episodic growth or rejuvenation of the Precambrian lower crust beneath the NCC is also revealed by U–Pb and Hf isotope data, resulting from the corresponding addition of juvenile materials from mantle to lower crust, with a mixing of the old crust with juvenile magma. This compositional modification of the lower crust resembles the compositional transformation from the refractory lithospheric mantle to a fertile one through the refractory peridotite – infiltrated melt reaction as revealed in the lithospheric mantle beneath the NCC. [Copyright &y& Elsevier]

The Alxa Block is considered part of the North China Craton, but the unambiguous Archean basement has not been reported. In this study, we present the first evidence of the Neoarchean rocks in the Beidashan area of the western Alxa Block. The petrographic and geochemical data show that these rocks are granodiorite with TTG (tonalite-trondhjemite-granodiorite) characteristics. Zircon U-Pb dating gave an age of 2522±30 Ma for the magmatic core and 2496±11 Ma for the metamorphic recrystallized rim. The near-identical age between the Latest Neoarchean magmatism and the high-grade metamorphism shows that these features were related to the same Latest Neoarchean-Earliest Paleoproterozoic tectonothermal event. The age-corrected ɛ( t) value is mainly between 0.4 and 4.9. The two-stage zircon Hf model age ranges from 2.7 to 3.0 Ga, suggesting that the Mesoarchean-Neoarchean (2.7-3.0 Ga) juvenile crust was reworked at the end of the Neoarchean in the western Alxa Block. These data suggest that the western Alxa Block experienced a Mesoarchean-Neoarchean crust growth and Latest Neoarchean-Earliest Paleoproterozoic tectonothermal event similar to the North China Craton. [ABSTRACT FROM AUTHOR]

Zircon U-Pb ages (SHRIMP and LA-ICPMS) and Lu-Hf isotope data (LA-ICPMS) are presented for two granite and two quartzite pebbles from the basal conglomerates of the Sijizhuang Formation in the Hutuo Group from the Wutai Mountains area in the North China Craton. These two granite pebbles give zircon Pb/Pb ages of 2513±8 Ma and 2527±8 Ma respectively, which are consistent with the emplacement ages of the Wangjiahui grey granite and Guangmingsi or Shifo granite in the Wutai Mountains. Detrital zircons from those two quartzite pebbles are mostly 2550-2490 Ma old with lesser number of 2800-2550 Ma grains, which is similar to the ages of detrital zircons from quartzites in the Gaofan Subgroup of the Neoarchean Wutai Group. Thus, the pebbles in the Hutuo Group basal conglomerates were derived locally from Wutai Mountains Neoarchean sources. Zircons from the Sijizhuang Formation conglomerate granite and quartzite pebbles mostly have positive ɛ( t) values, a minority with ɛ( t) values like model depleted mantle (DM) of the same age, but with most showing DM model ages 200-100 Ma. This indicates that most of the source materials were derived from the mantle within the previous 200 million years, whereas some are derived from 2550-2510 Ma juvenile crustal additions. This additional evidence suggests that in the North China Craton there was important initial polycyclic crustal formation and cratonization in the late Neoarchaean, prior to superimposed Palaeoproterozoic orogenic cycles. [ABSTRACT FROM AUTHOR]

The composition of single-grain detrital zircons is an effective provenance indicator of loess, and sheds new light on dust formation and transportation. Here we review the features of detrital zircons and their use as a provenance indicator, including internal structure, trace element, U-Pb age spectrum and Hf isotopic compositions, and present a case study from the Horqin sandy land and its surrounding loess. The loess samples have detrital zircon age peaks in range of 2600-2300, 2100-1600, and 600-100 Ma, of which the 2600-2300 Ma zircon grains mainly have positive ɛ( t) values (−3.4-8.7), the 2100-1600 Ma zircon grains mainly have negative ɛ( t) values (−10.1-6.8), and the 600-100 Ma zircon grains have a variable ɛ( t) values ranging from −21 to 15.9. The detrital zircon signatures of the loess are similar to the Horqin sandy land, but clearly different from the Chinese Loess Plateau and central-western deserts, implying that the loess is transported mainly from the Horqin sandy land in the Last Glacial period. Comparing these with neighboring tectonic units, we found that zircon populations at 2600-2300, 2100-1600, and 600-100 Ma with negative ɛ( t) values may come from the northeast North China Craton (NCC), and those at 600-100 Ma with positive ɛ( t) values may come from the east Central Asian Orogenic Belt (CAOB). It is estimated that the two sources contribute equally to the Horqin sandy land and the surrounding loess. [ABSTRACT FROM AUTHOR]

Abstract: The ca. 1525Ma igneous Mucajaí anorthosite–monzonite–granite (AMG) complex in northern Brazil is a rare manifestation of Mesoproterozoic intraplate magmatism in the northern Amazonian Craton. The complex comprises a two-phase rapakivi granite batholith with subordinate quartz–fayalite monzonites and syenites and the closely associated Repartimento anorthosite. Zircon U–Pb (ID–TIMS) geochronology reveals that the anorthosite (1526±2Ma), monzonite (1526±2Ma), and the main-phase biotite–hornblende granite (1527±2Ma) of the complex intruded the Paleoproterozoic (~1.94Ga) country rocks simultaneously at ~1526Ma and that the more evolved biotite granite is marginally younger at 1519±2Ma. Intraplate magmatism in the Mucajaí region was relatively short-lived and lasted 12million years (1529–1517Ma) at maximum. The Nd (whole-rock, ID–TIMS; εNd from −1.9 to −2.8), Hf (zircon, LAM-ICP-MS; εHf from −2.0 to −3.1), and O (zircon, SIMS; δ18O from 6.1 to 7.0‰) isotopic compositions of the studied rocks are fairly uniform but still reveal a small degree of isotopic heterogeneity in the Paleoproterozoic crust enclosing the complex. The small isotopic differences observed in the two types of rapakivi granites (biotite–hornblende granite and biotite granite) may result either from an isotopically heterogeneous lower crustal source or, more likely, from contamination of the granitic magma derived from a lower crustal source during prolonged residence at upper crustal levels. [Copyright &y& Elsevier]

Abstract: The tectonic evolution of the North China Craton (NCC) from the Late Mesoproterozoic to the Neoproterozoic has been unclear. This paper reports the results of LA–ICP–MS U–Pb dating and in situ Hf isotope analysis of detrital zircons from Neoproterozoic strata in the northern Jiangsu and southern Liaoning provinces of southeastern NCC, and we go onto discuss how these results help constrain the Late Precambrian evolution of the NCC. Most analyzed zircon grains exhibit oscillatory growth zoning, and they have relatively high Th/U ratios (>0.4) and positive Ce anomalies as well as negative Eu anomalies, all of which suggests a magmatic origin. The detrital zircons from the Xinxing and Jinshanzhai formations in northern Jiangsu Province give weighted mean ages of 1753, 1635, 1486, and 1121Ma, and 2515, 2305, 1856, 925, and 825Ma, respectively, and the detrital zircons from the Diaoyutai and Xingmincun formations in southern Liaoning Province give ages of 1745, 1619, 1484, 1175, and 1077Ma, and 1798, 1623, 1150, 1020, and 934Ma, respectively. These results, together with previously published ages, indicate that (1) the Neoproterozoic strata in the northern Jiangsu and southern Liaoning provinces were deposited during a period from the Late Mesoproterozoic to Neoproterozoic, and (2) the sediments in the Neoproterozoic strata were sourced mainly from igneous rocks of Late Paleoproterozoic, Mesoproterozoic, and Early Neoproterozoic age, as well as from the ancient Precambrian basement of the NCC. The concordia plots for 291 detrital zircon grains give three prominent age groups of 1.86–2.5, 1.5–1.8, and 0.9–1.2Ga. The detrital zircon ages of 1.86–2.5Ga in the Neoproterozoic strata tie in with most of the Precambrian tectonic–magmatic–thermal events that occurred in the NCC. Zircon ages of 1.6–1.8Ga can be linked to rift magmatism of Late Paleoproterozoic age in the NCC. The detrital zircon ages of 0.9–1.2Ga can be related to Grenville-aged magmatism in the southeastern NCC. The zircons show negative ɛ Hf (t) values (−8.8 to −0.1), suggesting that the source rocks were dominated by reworked ancient Precambrian crust. The positive ɛ Hf (t) values (+0.3 to +10.8) and Hf model ages indicate that growth of continental crustal occurred at ∼2.7Ga, ∼1.9Ga, and ∼1.5Ga in the southeastern NCC. [Copyright &y& Elsevier]

Abstract: The Lu-Hf isotopic composition of detrital zircons has been used to investigate the crustal evolution of the northern part of the West African Craton (WAC). The zircons were separated from six samples of siliciclastic sedimentary rocks from the main Neoproterozic stratigraphic units of the Anti-Atlas belt, from the Sirwa and Zenaga inliers. The data suggest that the north part of the WAC formed during three cycles of juvenile crust formation with variable amount of reworking of older crust. The younger group of zircons, with a main population clustering around 610Ma, has a predominant juvenile character and evidences of moderate mixing with Paleoproterozoic and Neoarchean crust, which supports that most igneous and metamorphic rocks where zircons originally crystallized were formed in an ensialic magmatic arc environment. The group of zircons in the age range 1.79–2.3Ga corresponds to the major crust forming event in the WAC: the Eburnian orogeny. The isotopic data indicate that the provenance area should represent a crustal domain that was separated from a mantle reservoir at ∼2050–2300Ma, and further evolved with a time-integrated 176Lu/177Hf of ∼0.01, characteristic of continental crust. The evolution of the Eburnian orogeny is, consequently, compatible with new crust formation in an island arc environment, the transition to a continental arc setting and a final continent–continent collision. The Lower Paleoproterozoic and Neoarchean evolution (2.3–2.75Ga) includes a group of detrital zircon ages that has not been identified up to now in the igneous or metamorphic rocks of the north WAC basement. Their Hf isotopic signature points to reworking of mainly juvenile Neoarchean crust with some Meso- to Palaearchean contributions. The significance of these ages is uncertain: they can represent a tectonothermal event not discovered yet in the Reguibat Shield or the zircons can be far traveled from an unknown source. [Copyright &y& Elsevier]

Abstract: Six samples of the Linglong granitic pluton from the southeastern margin of the North China craton yield similar Jurassic magmatic zircon U–Pb ages and evolved whole-rock Sr–Nd isotopic compositions. They are weakly peraluminous to strongly peraluminous, with A/CNK (molar Al2O3/[CaO+Na2O+K2O]) ratios of 1.05 to 1.3 except one sample with an A/CNK of 0.98. However, they have contrasting inherited zircon ages and magmatic zircon Hf and O isotopic compositions. Two samples have ~2.5Ga inherited zircons and high δ 18O magmatic zircons and are interpreted to be derived dominantly from the lower crust of the North China craton. Another two samples with dominantly Triassic inherited zircons and low δ 18O magmatic zircons are considered to be derived mainly from the subducted continental crust of the South China craton and the source was considered to be significantly depleted in 18O during Triassic metamorphism. The rest two samples have dominantly Neoproterozoic inherited zircons and intermediate δ 18O magmatic zircons and are also considered to be derived mainly from the subducted continental crust of the South China craton. But the source was not significantly depleted in 18O during Triassic metamorphism. The different lithologies, whole-rock ε Nd(t) and zircon ε Hf(t) between the samples also strongly support that they are derived from different sources. Although magmatic zircons from the six samples have variable δ 18O from 0.7 to 8.5‰ and ε Hf(t) from −27.6 to −11.8, individual samples have more limited ε Hf(t) and δ 18O. The δ 18O and ε Hf(t) of magmatic zircons from the samples indicate no contribution of mantle-derived magmas to the Linglong granites. This is supported by the fact of no coeval mantle-derived rocks in the region. The results suggest that large variations of ε Hf(t) and δ 18O do not necessarily indicate mixing between mantle- and crustal-derived magmas. Instead, they may reflect heterogeneity in the source. The granites are interpreted to result from partial melting of the thickened crust caused by Triassic subduction of the South China craton continental crust beneath the North China craton. Subsequent lithospheric extension and orogenic collapse are the most likely mechanism for the granites. [Copyright &y& Elsevier]

Abstract: Simultaneous in situ U–Pb dating, trace element and Hf isotopic analyses have been carried out on detrital zircons obtained from sandstones in the Neoproterozoic Jing’eryu Formation from the Eastern Block, North China Craton (NCC), with the aim of constraining the ages of magmatic and metamorphic events and hence the Precambrian crustal evolution of the NCC. Two groups of zircons, i.e., magmatic and metamorphic in origin, have been identified based on cathodoluminescence images, zircon Ti-temperatures and Th/U ratios. Zircon U–Pb dating shows two main magmatic events with ages of 2.55–2.47Ga and 1.80–1.70Ga, and four metamorphic events, with ages of 2.51–2.48Ga, 1.96–1.90Ga, 1.87–1.85Ga and ∼1.80Ga in the NCC. No zircons with ages of ∼3.8Ga have been identified in this study, indicating either these were covered at the time of deposition or the limited presence of 3.8Ga rocks in the NCC. The Hf isotopic data show the ∼2.5Ga magmatic zircons have variable ɛ Hf(t) values, including both positive and negative values and with crustal model ages of 2.7–2.9Ga, which can be interpreted to indicate mixed sources for their parental rocks, i.e., ancient crust (3.8Ga or 3.3Ga) and depleted mantle, implying significant continental crustal growth at ∼2.5Ga. However, Paleoproterozoic magmatic zircons all have negative ɛ Hf(t) and Archean Hf model ages, suggesting that their parental rocks were formed from recycled Archean materials. The widespread ∼2.5Ga metamorphism in the Eastern Block, coupled with extensive ∼2.5Ga magmatism and crustal growth, are consistent with a mantle plume beneath the Eastern Block of the NCC during the Neoarchean. Whereas, a progressive increase in ∼1.85Ga metamorphic zircon westward across the Eastern Block toward the Trans-North China orogen is best explained by collision between the Eastern and Western blocks at this time. [Copyright &y& Elsevier]

Abstract: Kimberlite, a deep-sourced ultramafic potassic rock, carries not only diamond, but also invaluable mantle xenoliths and/or xenocrysts, which are important for tracking the evolution of subcontinental lithospheric mantle (SCLM). However, it is challenging to accurately determine the emplacement age of kimberlite and its compositions of primary magma because of modifications by crustal and/or mantle contamination and post-emplacement alteration. This paper reports emplacement ages of diamondiferous kimberlites in Mengyin and Fuxian of the North China Craton (NCC) using three different dating methods. For Mengyin kimberlite, single-grain phlogopite Rb–Sr dating yields an isochron age of 485±4Ma, U–Th–Pb analyses on perovskite give a 238U–206Pb age of 480.6±2.9Ma and a 232Th–208Pb age of 478.9±3.9Ma, and baddeleyite yields a 207Pb–206Pb age of 480.4±3.9Ma. For Fuxian kimberlite, baddeleyite gives a 207Pb–206Pb age of 479.6±3.9Ma, indicating that the Paleozoic kimberlites in the NCC were emplaced at ~480Ma. Numerous lines of evidence indicate that the studied baddeleyites are xenocrysts from the SCLM, and can be used to constrain Hf isotope compositions (ε Hf(t)~−6) of the SCLM when kimberlite erupted. Combined with data from Mesozoic–Cenozoic mantle-derived rocks and xenoliths, the Hf isotope evolution trend of the SCLM beneath NCC before craton destruction was tentatively constructed, which suggested that the Archean SLCM was enriched by metasomatism at ~1.3Ga. Further Hf isotope investigations on additional SCLM-derived materials could be used to compare with the constructed Hf isotope evolution trend before craton destruction to determine when lithospheric thinning occurred. [Copyright &y& Elsevier]

Abstract: The Gascoyne Province lies at the western end of the Capricorn Orogen, and includes a range of Neoarchean to Paleoproterozoic gneisses and metasedimentary basins (the Glenburgh Terrane) that record the amalgamation of the Archean Pilbara and Yilgarn Cratons to form the West Australian Craton. New Lu–Hf zircon data, integrated with the existing framework of U–Pb zircon and monazite data, provide direct evidence for the punctuated assembly of the West Australian Craton as a result of two discrete pre-1950Ma collision/accretion events. First, 2555–2430Ma granitic gneisses of the Glenburgh Terrane, interpreted as being exotic to both the Pilbara and Yilgarn Cratons, collided with (or were accreted to) the southern margin of the Pilbara Craton during the 2215–2145Ma Ophthalmian Orogeny. The predominantly psammitic protoliths to the Moogie Metamorphics were deposited in a pro-foreland basin across the Glenburgh Terrane in response to this collision, with detrital zircon Lu–Hf signatures indicating significant Pilbara-type crust in the source region. The Lu–Hf isotopic signatures of magmatic zircons from granitic gneisses and granites of the 2005–1970Ma Dalgaringa Supersuite, and of detrital zircon from 2000 to 1955Ma-aged fore-arc deposits (Quartpot Pelite of the Camel Hills Metamorphics), indicate that the magmatic rocks formed in a continental margin arc, by the mixing of juvenile, mantle-derived material with older continental crust. The isotopic signature of this older crustal material is similar to that of the Glenburgh Terrane, suggesting that oceanic plate subduction occurred toward the north, under the southern, leading edge, of the Glenburgh Terrane. Although the arc was initiated at c. 2080Ma, the older parts (pre-2005Ma) are no longer exposed. Ocean basin closure and collision between a combined Pilbara Craton–Glenburgh Terrane and the Yilgarn Craton occurred during the latter part of the Glenburgh Orogeny between c. 1965 and c. 1950Ma. [Copyright &y& Elsevier]

Abstract: In order to understand the Precambrian crustal growth and reworking history of the North China Craton, in situ U-Pb and Lu-Hf isotope analyses were carried out on the detrital zircons from a well-preserved, nearly undeformed Proterozoic sedimentary section with time interval of 1.8–0.8Ga. Totally, 806 zircons separated from 7 samples collected from each representative stratigraphic unit were measured for U-Pb and Lu-Hf isotopic compositions, of which 430 grains yielded concordant U-Pb ages. The concordant zircons show three prominent age groups of 1.6–1.8Ga, 1.9–2.2Ga and 2.3–2.6Ga. Both positive and negative ɛHf(t) values were exhibited by zircons from all groups, suggesting both juvenile crust addition and crustal reworking for all age groups. The Hf crustal model ages of zircons reveal that the juvenile materials were continuously added to the crust between 4.0 and 2.0Ga with a prominent peak at 2.7–3.0Ga and a less significant peak at 3.1–3.4Ga. The juvenile contributions to the newly formed crust decrease stepwise through time, and crustal reworking has dominated over juvenile inputs to the continental crust since 2.6Ga. Compared with the detrital zircons from modern rivers running within the North China Craton, the sedimentary rocks contain more older zircons, implying the relatively poor preservation of Archean crustal rocks in modern river sand, and accordingly the weights of Archean crystallizations ages and crustal growth inferred from detrital zircons in modern river are significantly underestimated. The integrated studies of detrital zircons from both modern river sands and ancient sedimentary rocks are essential to decipher the early crustal growth history more faithfully. [Copyright &y& Elsevier]

Provenance data from Paleoproterozoic and possible Archean sedimentary units in the central eastern Gawler Craton in southern Australia form part of a growing dataset suggesting that the Gawler Craton shares important basin formation and tectonic time lines with the adjacent Curnamona Province and the Isan Inlier in northern Australia. U-Pb dating of detrital zircons from the Eba Formation, previously mapped as the Paleoproterozoic Tarcoola Formation, yields exclusively Archean ages (ca 3300-2530 Ma), which are consistent with evolved whole-rock Nd and zircon Hf isotopic data. The absence of Paleoproterozoic detrital grains in a number of sequences (including the Eba Formation), despite the proximity of voluminous Paleoproterozoic rock units, suggests that the Eba Formation may be part of a Neoarchean or early Paleoproterozoic cover sequence derived from erosion of a multi-aged Archean source region. The ca 1715 Ma Labyrinth Formation, unconformably overlying the Eba Formation, shares similar depositional timing with other basin systems in the Gawler Craton and the adjacent Curnamona Province. Detrital zircon ages in the Labyrinth Formation range from Neoarchean to Paleoproterozoic, and are consistent with derivation from >1715 Ma components of the Gawler Craton. Zircon Hf and whole-rock Nd isotopic data also suggest a source region with a mixed crustal evolution (εNd -6 to -4.5), consistent with what is known about the Gawler Craton. Compared with the lower Willyama Supergroup in the adjacent Curnamona Province, the Labyrinth Formation has a source more obviously reconcilable with the Gawler Craton. Stratigraphically overlying the Eba and Labyrinth Formations is the 1656 Ma Tarcoola Formation. Zircon Hf and whole-rock Nd isotopic data indicate that the Tarcoola Formation was sourced from comparatively juvenile rocks (εNd -4.1 to + 0.5). The timing of Tarcoola Formation deposition is similar to the juvenile upper Willyama Supergroup, further strengthening the stratigraphic links between the Gawler and Curnamona domains. Additionally, the Tarcoola Formation is similar in age to extensive units in the Mt Isa and Georgetown regions in northern Australia, also shown to be isotopically juvenile. These juvenile sedimentary rocks contrast with the evolved underlying sequences and hint at the existence of a large-scale ca 1650 Ma juvenile basin system in eastern Proterozoic Australia. [ABSTRACT FROM AUTHOR]

Abstract: The Trans-North China Orogen is a recently recognized continent–continent collisional belt along which the discrete Eastern and Western Blocks amalgamated to form the coherent basement of the North China Craton. However, there is a hot debate on the timing of the collision between the two blocks, with one school of thought arguing the collision occurred at 2.5Ga, whereas others believe it took place at ~1.85Ga. U–Pb ages and Hf isotopic data of detrital zircons from foreland basins in the Trans-North China Orogen can provide rigorous constraints on this controversial issue. One of such foreland basins is represented by the Yejishan Group in the Lüliang Complex in the middle sector of the western margin of the Trans-North China Orogen. The group consists of conglomerates, quartz wackes, sandstones and minor limestones, most of which contain large amounts of detrital zircons. CL images reveal that nearly all detrital zircons from the Yejishan Group possess oscillatory zoning, with Th/U ratios of 0.2–2.34, typical of an igneous origin. The 207Pb/206Pb ages of detrital zircons range between 3.24 and 1.81Ga, with most having Paleoproterozoic ages, of which the youngest group ages are around 1.87–1.81Ga. This indicates that the foreland basin in which the Yejishan Group was deposited must have formed not earlier than 1.87–1.81Ga, thus supporting the collision between the Eastern and Western Blocks at ~1.85Ga, not at ~2.5Ga. [Copyright &y& Elsevier]

Abstract: The evolution of the North China Craton (NCC) is well known for a marked 2.55–2.50Ga tectonothermal event. However, supracrustal and intrusive rocks of 2.75–2.70Ga are in fact widely distributed in the western Shandong Province, the most important area of Archaean basement in the eastern part of the NCC. This paper reports SHRIMP U–Pb dating and LA-ICPMS Hf isotopic composition of zircons from 2.75–2.70Ga supracrustal and trondhjemite–tonalite–granodiorite (TTG) rocks in that area. Three fine-grained (hornblende) biotite gneiss samples (known locally as leptynite, with meta-volcanic or volcanosedimentary rock protoliths) and five TTG samples have SHRIMP zircon U–Pb ages varying from 2.75 to 2.70Ga and 2.74 to 2.71Ga, respectively. Zircons from most of the samples have high positive ɛ Hf(t) values (+4.7 to +10.0) and t DM(Hf) ages (2.85–2.60Ga) similar to their zircon U–Pb ages. This indicates that the rocks represent largely juvenile crustal additions derived from depleted mantle only a short time before. However, some granitoids show ɛ Hf(t) zircon values of −13.6 to +5.1 and t DM(Hf) of 3.51–2.80Ga. Therefore, the strong 2.75–2.70Ga tectonothermal event in the western Shandong Province involved not only juvenile addition to the continental crust but also intracrustal recycling of older components. Combined with craton-wide data, it is shown that the NCC is similar to many other cratons around the world where tectonothermal events of ∼2.7Ga are well developed. However, the main difference is that in the NCC, superimposed ∼2.5Ga tectonothermal events were much stronger than in most other cratons. [Copyright &y& Elsevier]

Abstract: The Helanshan Complex is located at the westernmost segment of the Khondalite Belt, a continent–continent collisional belt along which the Yinshan Block in the north collided with the Ordos Block in the south to form the Western Block of the North China Craton. The complex consists of S-type granites and high-grade pelitic granulite/gneiss, felsic paragneiss, quartzite, calc-silicate rock and marble, together called the Khondalite Series rocks. LA-Q-ICP-MS U–Pb geochronology and LA-MC-ICP-MS Lu–Hf isotopic data of zircons, combined with cathodoluminescence (CL) imaging, enable the resolution of magmatic and metamorphic events that can be directed towards understanding the formation and evolution of the Khondalite Belt in the Western Block of the North China Craton. CL images reveal the coexistence of magmatic-type detrital zircons and metamorphic zircons in most of the Khondalite Series rocks, of which the metamorphic zircons occur as either single grains or overgrowth rims surrounding and truncating magmatic-type detrital zircon cores. LA-Q-ICP-MS U–Pb analyses on magmatic-type detrital zircons reveal two distinct age populations, with one in the Archaean (2.85–2.53Ga) and the other in the Palaeoproterozoic (2.2–2.0Ga), suggesting that the sedimentary protoliths of the Khondalite Series rocks in the Helanshan Complex must have been deposited at some time after 2.0Ga. The Hf analyses show that the Archaean detrital zircons possess negative εHf(t) values from −7.64 to −0.15 with depleted mantle model ages ranging from 3.34 to 3.10Ga. This implies the existence of a Paleo-Mesoarchaean (3.34–3.10Ga) crust in the Western Block, which underwent a recycling event in the period 2.85–2.53Ga. Nearly all Palaeoproterozoic (2.2–2.0Ga) detrital zircons possess positive εHf(t) values (0.86–9.38) with depleted mantle model ages of 2.45–2.15Ga, suggesting a significant crustal growth event in the Western Block in the Palaeoproterozoic. Metamorphic zircons yield two groups of age, with one at ~1.95Ga and the other at ~1.87Ga, of which the former is considered as the timing of the collision between the Yinshan and Ordos Blocks to form the Western Block, whereas the latter is consistent with the age of ~1.86Ga from two S-type granites which are considered to have formed by the partial melting of pelitic granulites/gneisses at the stage of the exhumation of the Helanshan Complex. [Copyright &y& Elsevier]

Abstract: The Gawler Craton forms the bulk of the South Australian Craton and occupies a pivotal location that links rock systems in Antarctica to those in northern Australia. The western Gawler Craton is a virtually unexposed region where the timing of basin development and metamorphism is largely unknown, making the region ambiguous in the context of models seeking to reconstruct the Australian Proterozoic. Detrital zircon data from metasedimentary rocks in the central Fowler Domain in the western Gawler Craton provide maximum depositional ages between 1760 and 1700Ma, with rare older detrital components ranging in age up to 3130Ma. In the bulk of samples, ɛ Nd(1700Ma) values range between −4.3 and −3.8. The combination of these data suggest on average, comparatively evolved but age-restricted source regions. Lu–Hf isotopic data from the ca 1700Ma aged zircons provide a wide range of values (ɛ Hf(1700Ma) +6 to −6). Monazite U–Pb data from granulite-grade metasedimentary rocks yield metamorphic ages of 1690–1670Ma. This range overlaps with and extends the timing of the widespread Kimban Orogeny in the Gawler Craton, and provides minimum depositional age constraints, indicating that basin development immediately preceded medium to high grade metamorphism. The timing of Paleoproterozoic basin development and metamorphism in the western Gawler Craton coincides with that in the northern and eastern Gawler Craton, and also in the adjacent Curnamona Province, suggesting protoliths to the rocks within the Fowler Domain may have originally formed part of a large ca 1760–1700Ma basin system in the southern Australian Proterozoic. Provenance characteristics between these basins are remarkably similar and point to the Arunta Region in the North Australian Craton as a potential source. In this context there is little support for tectonic reconstruction models that: (1) suggest components of the Gawler Craton accreted together at different stages in the interval ca 1760–1680Ma; and (2) that the North Australian Craton and the southern Australian Proterozoic were separate continental fragments between 1760 and 1700Ma. [Copyright &y& Elsevier]

Abstract: U–Pb dating and Hf isotope analyses were performed on detrital zircons from the Upper Permian sandstones in the Ordos and Jiyuan basins, with aims of defining the sediment provenance, and by inference, to determine the influence of the surrounding plates on the evolution of the North China Craton (NCC). Detrital Zircons from these two basins fall into three major groups based on their U–Pb ages: Phanerozoic, Paleoproterozoic, and Neoarchean. The youngest grain from every sample is only slightly younger than the real depositional age of strata. The Phanerozoic zircons from the Jiyuan basin (244–390Ma) show εHf (t) ranging from −30.3 to −1.3, suggesting a provenance from the Inner Mongolia Paleo-uplift (245–376Ma, εHf (t)=−18.9 to −1.7). A bi-modal distribution of ages and εHf (t) is noted for detrital zircons from the Ordos basin; one resembles that of the Jiyuan basin, the other is characterized by Early Paleozoic ages and relatively high εHf (t) values (−10.9 to 7.7). A hybrid source is thus inferred for the Ordos sediments; the Northern Qinling Orogen (428–478Ma, εHf (t)=−10.9–7.7) must have served as a source in addition to the Inner Mongolia Paleo-uplift source. This interpretation is consistent with the fact that the Northern Qinling Orogen was an active margin during the Early Paleozoic and suggests that the western part of the Northern Qinling Orogen was elevated relative to the center of the craton during the Late Paleozoic. It is likely that the Early Paleozoic arc-trench in the northern part of the Dabie Orogen was under-thrusted below the NCC due to the subduction of the Yangtze plate during the Triassic. The Inner Mongolia Paleo-uplift was strongly uplifted by subduction of the Paleo-Asian Ocean Plate underneath the northern NCC and functioned as a sediment source for the inner craton during the Late Paleozoic. These results reveal a heterogeneous pattern of destruction of the North China Craton, with its northern margin starting to be activated no later than Late Paleozoic. [Copyright &y& Elsevier]

Abstract: Geochronological, petrological and geochemical studies were performed on the granulite xenoliths from a Late Cretaceous basaltic breccia dike in Junan, Shandong province, eastern China. These xenoliths show close similarities to the Nushan granulite xenoliths from the southern margin of the North China Craton (NCC) and the Archean granulite terrains in terms of mineralogy and bulk rock compositions, but are quite different from the Hanuoba mafic granulite xenoliths from the northern NCC. In-situ zircon U–Pb age and Hf isotopic analyses, together with geochemical data reveal that the protolith of these xenoliths was formed around 2.3Ga ago, through assimilation–fractional crystallization of a mafic magma. P–T conditions of these xenoliths suggest that the lower crust beneath the Junan region reaches to a depth of 35km, which agree well with the result deduced from various geophysical methods. The consistent petrological and seismic Moho depths, the observed velocity structure and calculated velocity of these xenoliths imply the absence of underplating induced crust–mantle transition zone, which was well formed in the northern NCC. Compared to 40–50km depth of the lower crust in Early Jurassic, the lower crust beneath Junan extended to a depth of 30km in Late Cretaceous, suggesting that the lower crust of NCC was significantly thinned during Late Mesozoic. [ABSTRACT FROM AUTHOR]

Abstract: The ~1.74-Ga Damiao complex in the North China Craton consists of anorthosite (85%), norite (10%), mangerite (4%) and minor troctolite (<1%), all of which are cut by gabbroic and ferrodioritic dikes. The complex hosts abundant Fe–Ti–P oxide ores and has an emplacement sequence from anorthosite and norite to Fe–Ti–P oxide ores to mangerite. All of the different lithologies in the complex have similar light rare earth element (LREE)-enriched patterns and Nd isotopic compositions with ε Nd(t) values mostly within the range of −5.0 to −4.0. Average ε Hf(t) values of zircon are −4.7 for mangerite and −5.9 for norite. Plagioclase and clinopyroxene show a continuous range of composition from anorthosite and norite to Fe–Ti–P oxide ores to mangerite, suggesting that these lithologies formed by differentiation from a common parental magma. Gabbroic dikes in the Damiao complex are characterized by high Al2O3 (14.5–17.1 wt.%), Sr (~1000 ppm) and Mg#s [100 Mg/(Mg+Fe2+)]=56–73), similar to the high-Al gabbros parental to the Harp Lake and Laramie anorthosite complexes in North America. The high-Al gabbroic dikes of the Damiao complex may reflect the parental melt from which the complex formed, whereas the ferrodioritic dikes may represent residual melts after anorthosite crystallization from the high-Al gabbroic magma. The high-Al gabbros have incompatible element ratios (Zr/Nb=14–24; La/Nb=3.6–4.8), which differ significantly from those of nearby coeval, mantle-derived, mafic dike swarms and volcanic rocks but are similar to those of the lower crust. Their zircon ε Hf(t) and whole-rock ε Nd(t) compositions plot along the evolution lines of the ~2.5 Ga Archean rocks in the North China Craton, suggesting that the Damiao complex was derived from an ancient lower crust. Exceptionally high temperatures and high-degrees of melting (>75%) would have been required to form the parental high-Al gabbroic magma from the lower crust. We propose that the crustal rocks were dragged into the upper mantle during amalgamation of the North China Craton, where the ambient temperature was high enough (>1271 °C at 12 kbar) to cause extensive melting, producing a deep-seated magma chamber. The melt then evolved through polybaric crystallization, producing anorthositic magmas with abundant suspended plagioclase that were finally injected at mid-crustal depth to form the Damiao complex. [Copyright &y& Elsevier]