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The Ghorveh batholith, located in the central part of the Sanandaj–Sirjan Zone (SSZ), Iran, preserves several sequences of Mesozoic plutonic and volcanic rocks. This study presents systematic analyses of the calc‐alkaline granites and monzodiorites from the southern part of the Ghorveh pluton. The granites are metaluminous to slightly peraluminous with A/CNK ratios of 0.97–1.02, indicating an A‐type granitic affinity. High Rb, Th, and K and low Sr, P, and Ti concentrations indicate an involvement of crustal materials. Whole‐rock negative εNd(t) values and relatively high TDM1 model ages support a continental crustal source. Thus, the granites are of fractionated A‐type in composition produced by partial melting of crustal materials. The monzodiorites have incompatible trace element patterns with enrichment in light rare earth elements (LREEs) and large‐ion lithophile elements (LILEs) relative to heavy rare earth elements and high‐field strength elements. This combined with the high Mg# values and the positive εNd and εHf(t) values, indicate a mantle‐derived origin. Dating results show that the granites and monzodiorites have uniform crystallization ages of ~150 Ma. Previous results and our new data suggest that the Jurassic subduction of Neo‐Tethyan Oceanic crust under the Eurasian continent was followed by slab rollback that induced back‐arc extension. Heat transfer from arc magmas increased the degree of decompressional melting in the thinned lithosphere. Melting of the presumably homogeneous crust was concurrent with emplacement of the intermediate composition magmas. Consequently, we propose that the Ghorveh area of the central SSZ developed in a supra‐subduction extensional phase during the Late Jurassic. [ABSTRACT FROM AUTHOR]

• 2.56–2.33 Ga magmatism were revealed in the Taihua Complex (THC). • The formation of 2.56–2.50 Ga TTGs in THC was related to amalgamation of micro-blocks. • The formation of ∼ 2.35 Ga granitic rocks in THC was related to a worldwide rifting event. • A tectonic transition from compression to extension occurred during the late Neoarchean. • Multistage crustal growth, reworking and stabilization were record in the southern NCC. The Archean-Paleoproterozoic Taihua Complex, extending from east to west along the southern margin of the North China Craton (NCC), is an ideal window to understand the tectonic evolution of the early Earth. Here we present new data on petrology, zircon geochronology, whole-rock geochemistry and isotopes of TTGs, granitic gneisses and felsic leucosomes of migmatites from the Taihua complex in the Xiaoqinling area. Zircon LA-ICP-MS analyses of rocks yield the formation ages of 2564–2503 Ma for TTGs, 2481–2476 Ma for felsic leucosomes and 2359–2334 Ma for granitic gneisses, respectively. The zircon Lu-Hf isotopes suggest that crustal growth occurred in the late Neoarchean and crustal reworking occurred in the end of Neoarchean and the early Paleoproterozoic. The TTG gneisses are characterized by high Na 2 O/K 2 O, La/Yb, Sr/Y and low Nb/Ta ratios, and they were likely generated by partial melting of subducted juvenile oceanic crust with garnet or amphibole in residuals, a mechanism similar to the slab melting model. Both the felsic leucosomes and granitic gneisses have high SiO 2 contents and various Hf isotopic compositions, and they probably were formed in an extensional setting, attributing to partial melting as well as mixing of the preexisting TTG suite. Statistically, we report a major transitional phase in the tectonic milieu of the southern NCC from compression to extension during the late Neoarchean (ca. 2.57–2.42 Ga). The compressional tectonics can be attributed to amalgamation of micro-continental blocks during the late Neoarchean (ca. 2.57–2.5 Ga) as the leading period of crustal growth and associated multistage TTG magmatism. In contrast, the extensional phase occurred during the end of Neoarchean (ca. 2.5–2.42 Ga) that may represent the end of cratonic stabilization period and formation of large amounts of K-rich granitic rocks, widespread high-grade metamorphism and migmatites. Additionally, the formation of a large amount of crust-derived granites and mafic dykes during the early Paleoproterozoic in southern NCC reflect another stage (ca. 2.36–2.24 Ga) of crustal extension, which represents an episode of initial worldwide rifting events probably linking to the great oxygen event (GOE). Therefore, the present study proposes a new profile on multi-stage crustal growth/reworking and craton stabilization during Neoarchean-Paleoproterozoic period along the southern NCC, and provides useful insights on complex and heterogeneous evolutionary processes of early Earth. [ABSTRACT FROM AUTHOR]

Highlights • The granulite-facies metamorphic rocks have a large spread in metamorphic ages (2036–1962 Ma). • Zircon Hf isotopes suggest a long-lived reworking of the preexisting crust. • The source of the granulite-facies metamorphic rocks is likely the garnet-bearing middle crust. • The Dunhuang Block was possibly an active continental margin during the Paleoproterozoic. Abstract The key to understanding the generation of mantle-derived magma and the formation of new continental crust is the recognition of the granulite-facies metamorphism, associated partial melting, and coeval magmatism that are documented in active continental margins. We firstly present a combined analysis of petrography, mineral chemistry, zircon U-Pb ages and hafnium (Hf) isotopes, in addition to whole-rock geochemistry on the garnet-biotite gneisses (Grt-Bi gneisses) and mafic granulites from the Aketashitage area, southeastern Tarim Craton. The implications of this analysis are discussed with respect to the thermal and tectonic evolution of the Tarim Craton. The Grt-Bi gneisses and mafic granulites are strongly peraluminous in composition and have flat REE patterns with negative Eu anomalies that are identical to those from the middle crust but higher than lower continental crust. Both the Grt-Bi gneisses and the mafic granulites have negative Nb-Ta anomalies, slightly positive Zr-Hf anomalies, and pronounced positive spikes in U and Pb. The characteristics in whole-rock geochemistry and mineral compositions indicate that the Grt-Bi gneisses and mafic granulites have the same source locality, which is most likely the garnet-bearing middle crust. The retrograde metamorphic P-T estimates for the Grt-Bi gneisses and mafic granulites are T = 574 °C; P = 7.0 kbar and T = 715 °C; P = 7.0 kbar, respectively. SIMS zircon U-Pb dating results reveal a large spread in metamorphic ages (2036–1962 Ma) for these granulite-facies rocks, interpreted to be the consequence of a large amount of magmas being added to the crust in an uninterrupted manner. Zircon Hf isotopes are characterized by variable but mostly negative ε Hf (t) values (−18.2 to −0.6), reasonably uniform Hf isotopic compositions, and highly variable T DM C model ages between 2628 and 3599 Ma, representing a long-lived reworking of the preexisting crust. Our data, along with available geological evidences, lead us to propose a model for the evolution of the Dunhuang Block in the Paleoproterozoic. That is, the southeastern margin of the Tarim Craton, the Dunhuang Block was possibly an active continental margin during the Paleoproterozoic. The steep subduction of oceanic slab resulted in the thickening of the continental crust, which in turn caused the crust anatexis. The increase in asthenosphere high heat flow and the intrusion of mantle-derived magma induced extensive heating, which preceded the granulite-facies metamorphism and coeval magmatism in the middle crust of the southern Tarim Craton. [ABSTRACT FROM AUTHOR]

Comparisons between the tectonic units on two sides of the sinistral ENE-striking Altyn Tagh Fault (ATF) are important tracers to find out the corresponding relationships among different terranes. This study focuses on the tectonic units along the eastern segment of the ATF. The Paleoproterozoic Beidahe Group in the mid-Qilian terrane, south side of the eastern segment of the ATF, is mainly composed of metasedimentary rocks and amphibolites. These rocks are petrologically and mineralogically similar to those from the Dunhuang Group, north side of the eastern segment of the ATF. The detrital zircon U-Pb ages indicate that the protolith sediments of the Beidahe metasedimentary rocks were mainly sourced from a provenance dominated by magmatic rocks in ages of 2.85–2.55 Ga, 1.70–1.55 Ga and 1.42–1.03 Ga. This sedimentary sequence was deposited no earlier than 1.03 Ga as passive continental margin deposits. Geochemical and zircon U-Pb and Lu-Hf isotopic data suggest that the Neoarchean-Mesoproterozoic basement rocks from the Tarim Craton most likely provide the majority of source materials for their protolith. Amphibolites from the Beidahe Group have high total Fe 2 O 3 and Al 2 O 3 contents but low Mg# values, indicating a high degree of compositional evolution and contamination of the older crust. They have flat REE patterns but positive LILE and negative Nb-Ta and Ti anomalies, suggesting a back-arc basin basalts (BABBs) affinity for their protolith. The amphibolites have a crystallization age of 1.61 Ga and zircon ε Hf (t) values ranging from −7.7 to +10.6. The zircon ε Hf (t) values and whole-rock ε Nd (t) values indicate an involvement of juvenile and pre-existing old materials in the formation of their parental magmas. Comparisons between the Beidahe and Dunhuang Groups indicate that the metasedimentary rocks from these two groups are both sourced from the Tarim Craton but have different depositional ages, and that the amphibolites have similar crystallization ages but different tectonic settings for their source rocks. The field relationships and geochemical and geochronological characteristics of the metasedimentary rocks and amphibolites from the Beidahe Group support the interpretation that the observed recent proximity of these two rock complexes might be the result of tectonic juxtaposition rather than a primary intrusive contact. [ABSTRACT FROM AUTHOR]

Garnet-bearing mafic granulites and amphibolites from the Hongliuxia area of the southern Dunhuang orogenic belt, northwestern China, commonly occur as lenses or boudinages enclosed within metapelite or marble, which represent the block-in-matrix feature typical of orogenic mélange. Three to four generations of metamorphic mineral assemblages are preserved in these rocks. In the high-pressure amphibolites, prograde mineral assemblages (M1) occur as inclusions (hornblende + plagioclase + quartz ± chlorite ± epidote ± ilmenite) preserved within garnet porphyroblasts, and formed at 550–590 °C and 7.7–9.2 kbar based on geothermobarometry. The metamorphic peak mineral assemblages (M2) are composed of garnet + hornblende + plagioclase + quartz + clinopyroxene, as well as titanite + zircon + rutile + apatite as accessory minerals in the matrix, and are estimated to have formed at 640–720 °C and 14.1–16.0 kbar. The first retrograde assemblages (M3) are characterized by “white-eye socket” symplectites (hornblende + plagioclase + quartz ± biotite ± epidote ± magnetite) rimming garnet porphyroblasts, which formed at the expense of the garnet rims and adjacent matrix minerals during the decompression stage under P – T conditions of 610–630 °C and 5.6–11.8 kbar. The second retrograde assemblages (M4) are intergrowths of actinolite and worm-like quartz produced by the breakdown of the matrix hornblendes, and formed under P – T conditions of ∼490 °C and ∼2.8 kbar. For the high-pressure mafic granulites, the prograde assemblages (M1) are represented by plagioclase + quartz preserved within the garnet porphyroblasts. The metamorphic peak assemblages (M2) are garnet + matrix minerals (clinopyroxene + plagioclase + quartz + hornblende + rutile + zircon) and were estimated to have formed at ∼680 °C and ∼15.4 kbar. The retrograde assemblages (M3) are characterized by fine-grained patches of hornblende + plagioclase + quartz rimming the garnet porphyroblasts, as well as hornblende rimming clinopyroxene in the matrix, and were inferred to have formed at ∼620 °C and ∼4.2 kbar. For the metapelitic gneiss, the metamorphic peak assemblages are the garnet porphyroblasts plus the matrix minerals (biotite + plagioclase + quartz + ilmenite + zircon), which were estimated to have formed at ∼630 °C and ∼8.9 kbar. The mafic granulites and amphibolites record fairly similar clockwise P–T paths that include nearly isothermal decompression processes, which suggest that they experienced subduction and subsequent rapid tectonic exhumation. SIMS and LA-ICP-MS U–Pb dating of zircons and 40Ar/39Ar dating of hornblende suggest that the metamorphism occurred at ∼430–390 Ma. Field occurrences, different protolith ages of the mafic granulites and amphibolites, and the considerable gap in peak P – T conditions between the amphibolite and mafic granulite boudinages and their country rock may suggest a mélange accumulation process during the Paleozoic caused by the Silurian–Devonian orogeny, which is possibly associated with the closure of the Liuyuan ocean, a branch of the Paleo-Asian ocean near the southern Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]