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In situ zircon U-Pb geochronological and Lu-Hf isotope studies of detrital zircons from Late Mesoproterozoic to Early Neoproterozoic sedimentary units on the southwestern margin of the Yangtze Block have important implications for the tectonic evolution of the Yangtze Block. The Huili Group contains zircons whose ages are mainly Late Archean to Mesoproterozoic (2 650–2 450, 2 100–1 800, and 1 350–1 150 Ma). The Dengxiangying Group has one major age population of 1 900–1 600 Ma, and two subordinate age populations of 1 350–1 100 and 2 300–2 000 Ma. Yanbian Group sedimentary rocks have a zircon age population mainly in the range of 970–850 Ma, contemporaneous with the ages of widespread arc-related magmatism in the western Yangtze Block. Combining these results with previous work, the Huili and Dengxiangying groups were most likely deposited during ca. 1 160 to 1 000 Ma in an intra-continental rift basin setting, while the Yanbian Group accumulated during >920 to 782 Ma in a back-arc basin setting at the southwestern margin of the Yangtze Block. In addition, all these results further suggest a tectonic transition from a continental rift basin to a convergent environment at the southwestern margin of the Yangtze Block at 1 000–970 Ma. [ABSTRACT FROM AUTHOR]

The Ordos Basin's southern part is a composite zone made up of numerous continental blocks and has long been influenced by surrounding tectonism. However, only a few studies have investigated the existence of southern provenance supply and the basin's southern boundary in the Middle Jurassic Zhiluo Formation. Based on sandstone detrital zircon U-Pb dating and zircon rare earth element analyses, net-sand ratio maps, paleocurrent direction and the field outcrop survey, this study establishes the source area and boundary of the Zhiluo Formation in the southern basin, and discusses the tectonic events. The study shows that the four main age peaks in the detrital spectra occurs at 2283 Ma, 1788 Ma, 432.5 Ma and 218.7 Ma, with a few of the zircons dated at 794.5–1235.2 Ma. The North Qilian orogenic belt (N-QLOB), the western part of the North Qinling orogenic belt (NQOB), and the southern margin of the North China Block (SNCB) contributed to the provenance. According to an integrated analysis of the provenance and tectonic background of continental blocks in the basin's southern margin, the boundary of the basin in the depositional period of the Zhiluo Formation should reach the N-QLOB in the southwest, the NQOB in the south, and the Sanmenxia–Lushan fault belt in the southeast. On the basis of the aforementioned findings, the tectonic evolution of the continental blocks at the southern periphery of the Ordos Basin was restored. [ABSTRACT FROM AUTHOR]

Junggar Basin is an important exploration zone for sandstone‐hosted uranium deposits in north‐west China. However, neither the provenance of the host sandstone nor the uranium supply capacity of the potential source rocks have been well evaluated. To determine the provenances of the Mesozoic to Cenozoic sandstone grains and to evaluate relationships between the uranium source and the detritus provenances, a field investigation was performed at the Honggou section in the southern Junggar Basin. U–Pb geochronology and Hf isotopes were obtained from populations of detrital zircons from Jurassic through Palaeogene sandstones. The detrital zircon U–Pb ages display three main groups: 145–190 Ma, 250–360 Ma, and 360–460 Ma. The detrital zircon age distributions and the Hf isotopic characteristics of the sandstones correspond to different igneous rock units within the North and Central Tianshan Mountains. Therefore, the changes in the relative proportions of the zircon age populations indicate that there were major shifts of the provenance areas for the sandstones throughout the Early Jurassic to Palaeogene interval. The majority (92%) of Hf isotope εHf(t) values are positive and in the range of +0.7 to +15.5, which indicates that the majority of the zircons had crystallized in igneous rocks that were mainly derived from juvenile crust or depleted mantle. The majority (93%) of the two‐stage model ages (TDM2) are less than 1.8 Ga, thereby indicating the source of the majority of the igneous rocks was from the melting of ancient Meso‐Proterozoic juvenile crust. Carboniferous–Permian intermediate‐felsic igneous rocks in the Tianshan Mountains may be the primary source of released mobilized uranium and uranium‐enriched siliciclastics into the southern Junggar Basin. This study will assist in future uranium prospecting in this region. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the southwestern Yangtze Block during the Early Neoproterozoic period is still controversial because of the limited quantities of 1 000–860 Ma magmatic rocks. In this study, our new LA-ICP-MS zircon U-Pb dating results demonstrate that the Yanbian granodiorites in the southwest Yangtze Block were emplaced at 894.6±7.4 Ma, representing the product of an 894 Ma magmatism. The Yanbian granodiorites are metaluminous to weak peraluminous with A/CNK values of 0.8–1.1, resembling I-type granitoids. They are characterized by right-inclined REE patterns with moderate to insignificant negative Eu anomalies (δEu=0.6–0.9). Their primitive mantle-normalized trace element patterns are characterized by depletion of Nb, Ta and Ti and weakly enrichment of Th. Considering the positive whole-rock εNd(t) (+5.8 to +6.8), we propose that these granodiorites originated from the partial melting of juvenile mafic lower crust. The Yanbian I-type granitoids have low Y and Nb contents similar to volcanic arc igneous rocks in the Y-Nb plot for tectonic discrimination. In conclusion, Early Neoproterozoic Yanbian granodiorites have generated in a compression setting in an active continental margin. Together with previous studies from the southwestern Yangtze Block, we suggest that the 894 Ma subduction-related Yanbian granodiorites represent the early stage of subduction at the southwestern margin of the Yangtze Block. [ABSTRACT FROM AUTHOR]

This paper presents the results of combined studies of geochronology, geochemistry, whole rock Sr‐Nd and zircon Hf‐O isotopes carried out upon the rhyodacite and ignimbrite of Shangshu village, Shangyu town and Shanghupeng village of Jiangshan City in Zhejiang Province, along the northwestern side of the Jiangshan–Shaoxing suture. SHRIMP zircon U‐Pb dating of samples in the three areas yielded weighted mean 206Pb/238U ages of 842.8 ± 6.9 Ma and 850.0 ± 7.3 Ma, 839 ± 9 Ma and 832.2 ± 8.1 Ma, 828.3 ± 8.5 Ma and 836.9 ± 9.9 Ma, respectively. These ages are older than the volcanic rocks of the Shangshu Formation dated at around 780 Ma distributed in Fuyang City, Hangzhou City, Kaihua County, etc. The volcanic rocks generally have high SiO2 (54.08–76.80 wt%) and Al2O3 (12.40–21.31 wt%), low Fe2O3 (0.68–8.92 wt%), MgO (0.29–2.49 wt%), CaO (0.12–2.86 wt%), TiO2 (0.10–1.59 wt%) and P2O5 (0.01–0.39 wt%), with variable total alkalis (K2O + Na2O =5.42–8.29 wt%). There exists a clear negative correlation between SiO2 and P2O5. The volcanic rocks have A/CNK ratios of 1.03–2.77 and thus are peraluminous. They are characterized by enrichment in LREE, Rb, Ba, Zr, Hf, K, Th, La, U and depletion in Nb, Sr, P, Ti, with distinct LREE and HREE fractionation of (La/Yb)N values of 5.68–11.67, and with a moderate negative Eu anomaly (&Eu=0.58–0.89). Whole‐rock geochemical data shows that the Jiangshan volcanic rocks are possibly I‐type granitic rocks, even though they have some characteristics of A&S‐type granites due to the magma fractional crystallization and water‐rock interaction. Zircon δ18O values are 3.97‰–5.49‰ (average 4.50‰), 2.90‰–5.21‰ (average 4.32‰) for ignimbrite from Shangshu village section, and Shanghupeng village section, respectively. They are slightly lower than the average δ18O values of igneous zircons in equilibrium with mantle magmas (5.3 ± 0.6‰ (2σ)), the lower δ18O value also demonstrating the presence of high temperature water‐rock interactions. The ignimbrite rocks have positive ∊Nd(t) (4.02, 3.37, 3.91, 4.74, 2.85, 4.39, totals from the three areas) and ∊Nd(t) (in‐situ zircon) (4.3–14.6, a weighted mean of 8.4; 6.6–12.7, a weighted mean of 9.0; 8.1–12.0, a weighted mean of 9.5, respectively, from the three areas). In conjunction with the trace element studies, they indicate that the source region of the Jiangshan volcanic rocks was mainly composed of juvenile lower crustal material, mixed with some mantle‐sourced magma. Detailed elemental and isotopic data suggest that the Jiangshan volcanic rocks were formed in a continental arc setting. There is a series of ca. 860–830 Ma volcanic rocks formed in a back‐arc extensional setting in the southern margin of the eastern Jiangnan Orogen, along the northwest side of the Jiangshan–Shaoxing suture. The first stage rift‐related anorogenic magmatism may have occurred as early as ca. 860 Ma in the eastern Jiangnan Orogen. [ABSTRACT FROM AUTHOR]

This paper presents age and geochemical data of a recently identified Late Paleozoic volcanic sequence in central Jilin Province, with aims to discuss the petrogenesis and to constrain the tectonic evolution of the Central Asian Orogenic Belt in this area. Firstly, the volcanic rocks have zircon U‐Pb ages of 290–270 Ma. Secondly, they are characterized by (a) ranging in composition from the low‐K tholeiite series to high‐K calc‐alkaline series; (b) enrichment in light rare earth elements and depletion of heavy rare earth elements, with negative Eu anomalies; and (c) negative Nb, Ta, and Ti anomalies. Finally, the volcanic rocks yield ∊Hf(t) values of +7.1 to +17. These data suggest that the central Jilin volcanic rocks were possibly derived from predominant partial melting of a depleted lithospheric mantle that might have been modified by subducted slab–derived fluids. Combined with previous studies, the Late Paleozoic–Early Mesozoic magmatism in Central Jilin can be divided into two stages: (a) a volcanic arc stage (290–270 Ma) represented by low‐K to high–K, tholeiite to calc–alkaline plutons and (b) a syn–collisional stage (260–240 Ma) represented by high‐K calc–alkaline I‐type granites. Furthermore, the timing and the tectonic setting of the above magmatic rocks show that the arc was probably produced by the northward subduction of the Paleo‐Asian Ocean and that the final closure of the Paleo‐Asian Ocean occurred prior to the Early Triassic. [ABSTRACT FROM AUTHOR]

We undertook U-Pb-Hf isotope testing of detrital zircons from Late Paleozoic sedimentary rocks in the Jilin Province, NE China, with the aim of constraining the tectonic evolution of eastern Central Asian Orogenic Belt. The age populations of the detrital zircons from the sandstone of the Jiefangcun Formation in the Songliao Block are ~2234, ~1782, ~1030–921, ~817, ~540, and ~381–254 Ma, whereas those of the zircons from the greywacke of the Permian Kedao Formation in the Songliao Block yield are ~2436, ~1905, ~1692, 1146–1170, ~554–498, and ~342–255 Ma. Combined Hf isotope characteristics, these ages reveal that: (1) rocks from the Jiefangcun and Kedao formations were deposited after 254 and 255 Ma, respectively; (2) these formations were sourced mainly from the Songliao Block and the Jiamus Terrane in the eastern CAOB and to a lesser amount, from the northern margin of the NCC; and (3) it appears that several remnants of ancient Precambrian basement occur adjacent to these Late Paleozoic strata that occur within the microcontinental blocks. Detrital zircons from the silty sandstone of the Miaoling Formation in the western margin of the Khanka Terrane yield peak age populations of 508–476, 463–396, and 348–258 Ma, having similar εHf(t) values to those obtained from zircons within the Jiamusi Terrane. These data indicate that (1) deposition of the Miaoling Formation in the western margin of the Khanka Terrane had started by 258 Ma, and (2) these sediments were sourced mainly from the Jiamusi Terrane and local magmatic rocks. The widespread occurrence of detrital zircons with ages of 480–550 Ma and positive εHf(t) values within the Late Paleozoic strata in the Songliao Block and the Jiamusi–Khanka Terrane, indicates that the amalgamation of these blocks took place during the middle stage of the Paleozoic, probably after the Silurian, prior to the Late Permian. [ABSTRACT FROM AUTHOR]

The article discusses the research on the discovery of crystalline basement rocks at Yangtze Block in Southern China and mentions its geological significance in China. Topics include the use of uranium-lead dating to analyse isotopic composition of zircons from the granitic gneiss, the geochronology data provides tectonic activities in Yunnan Province, China, and the cathodoluminescence images of the rocks.