scholarly journals Comparison of Magma Oxygen Fugacity and Zircon Hf Isotopes between Xianglushan Tungsten-Bearing Granite and Late Yanshanian Granites in Jiangxi Province, South China

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 106
Author(s):  
Xing-Yuan Li ◽  
Jing-Ru Zhang ◽  
Chun-Kit Lai
Keyword(s):  
Oxygen Fugacity ◽  
South China ◽  
Granitic Magma ◽  
Geochemical Data ◽  
Jiangxi Province ◽  
Magmatic Zircon ◽  
Late Mesozoic ◽  
Icp Ms ◽  
T Values ◽  
Southern Jiangxi Province

Jiangxi Province (South China) is one of the world’s top tungsten (W) mineral provinces. In this paper, we present a new LA-ICP-MS zircon U-Pb age and Hf isotope data on the W ore-related Xianglushan granite in northern Jiangxi Province. The magmatic zircon grains (with high Th/U values) yielded an early Cretaceous weighted mean U-Pb age of 125 ± 1 Ma (MSWD = 2.5, 2σ). Zircon εHf(t) values of the Xianglushan granite are higher (−6.9 to −4.1, avg. −5.4 ± 0.7) than those of the W ore-related Xihuanshan granite in southern Jiangxi Province (−14.9 to −11.2, avg. −12.5 ± 0.9), implying different sources between the W ore-forming magmas in the northern and southern Jiangxi Province. Compiling published zircon geochemical data, the oxygen fugacity (fO2) of the late Yanshanian granitic magmas in Jiangxi Province (the Xianglushan, Ehu, Dahutang, and Xihuashan plutons) were calculated by different interpolation methods. As opposed to the W ore-barren Ehu granitic magma, the low fO2 of the Xianglushan granitic magma may have caused W enrichment and mineralization, whilst high fO2 may have led to the coexistence of Cu and W mineralization in the Dahutang pluton. Additionally, our study suggests that the absence of late Mesozoic Cu-Mo mineralization in the Zhejiang, Jiangxi, and Anhui Provinces (Zhe-Gan-Wan region) was probably related to low fO2 magmatism in the Cretaceous.

scholarly journals Subduction of a rifted passive continental margin: the Pohorje case of Eastern Alps–constraints from geochronology and geochemistry

2020 ◽  
Vol 113 (1) ◽  
Author(s):  
Ruihong Chang ◽  
Franz Neubauer ◽  
Yongjiang Liu ◽  
Johann Genser ◽  
Wei Jin ◽  
...  
Keyword(s):  
Continental Crust ◽  
Rift Zone ◽  
Eastern Alps ◽  
Granitic Magma ◽  
Geochemical Data ◽  
Icp Ms ◽  
Hp Metamorphism ◽  
Two Samples ◽  
Ultramafic Cumulates ◽  
T Values

Abstract This study presents geochronological and geochemical data from newly dated Permian granitic orthogneisses associated with the Eclogite-Gneiss unit (EGU) from the southernmost part of the Austroalpine nappe stack, exposed within the Pohorje Mountains (Slovenia). LA-ICP-MS zircon U–Pb ages of two samples of the augen-gneisses are 255 ± 2.2 Ma and 260 ± 0.81 Ma, which are interpreted as the age of magmatic crystallization of zircon. In contrast, all round zircons from leucogneisses give Cretaceous ages (89.3 ± 0.7 Ma and 90.8 ± 1.2 Ma), considered as the age of UHP/HP metamorphism. The round zircons overgrew older euhedral zircons of Permian and rare older ages tentatively indicating that these rocks are of latest Permian age, too. Zircon εHf(t) values of the four orthogneiss samples are between − 13.7 and − 1.7 with an initial 176Hf/177Hf ratio ranging from 0.282201 to 0.282562; T DM C is Proterozoic. The augen-gneisses show geochemical features, e.g. high (La/Lu)N ratios and strong negative Eu anomalies, of an evolved granitic magma derived from continental crust. The leucogneisses are more heterogeneously composed and are granitic to granodioritic in composition and associated with eclogites and ultramafic cumulates of oceanic affinity. We argue that the Permian granitic orthogneisses might be derived from partial melting of lower crust in a rift zone. We consider, therefore, that segment of the EGU is part of the distal Late Permian rift zone, which finally led to the opening of the Meliata Ocean during Middle Triassic times. If true, the new data also imply that the Permian stretched continental crust was potentially not much wider than ca. 100 km, was subducted and then rapidly exhumed during early Late Cretaceous times.

Origin of the Ordovician Mansehra granite in the NW Himalaya, Pakistan: constraints from Sr–Nd isotopic data, zircon U–Pb age and Hf isotopes

2018 ◽  
Vol 481 (1) ◽  
pp. 277-298 ◽  
Author(s):  
Masatsugu Ogasawara ◽  
Mayuko Fukuyama ◽  
Rehanul Haq Siddiqui ◽  
Ye Zhao
Keyword(s):  
Granitic Magma ◽  
Geochemical Data ◽  
Large Contribution ◽  
Crustal Material ◽  
Sr Isotope ◽  
Nw Himalaya ◽  
Nd Isotope ◽  
Isotope Data ◽  
Late Neoproterozoic ◽  
T Values

AbstractThe Mansehra granite in the NW Himalaya is a typical Lesser Himalayan granite. We present here new whole-rock geochemistry, Rb–Sr and Sm–Nd isotope data, together with zircon U–Pb ages and Hf isotope data, for the Mansehra granite. Geochemical data for the granite show typical S-type characteristics. Zircon U–Pb dating yields 206Pb/238U crystallization ages of 483–476 Ma. The zircon grains contain abundant inherited cores and some of these show a clear detrital origin. The 206Pb/238U ages of the inherited cores in the granite cluster in the ranges 889–664, 1862–1595 and 2029 Ma. An age of 664 Ma is considered to be the maximum age of the sedimentary protoliths. Thus the Late Neoproterozoic to Cambrian sedimentary rocks must be the protolith of the Mansehra granitic magma. The initial Sr isotope ratios are high, ranging from 0.7324 to 0.7444, whereas the εNd(t) values range from −9.2 to −8.6, which strongly suggests a large contribution of old crustal material to the protoliths. The two-stage Nd model ages and zircon Hf model ages are Paleoproterozoic, indicating that the protolith sediments were derived from Paleoproterozoic crustal components.

Neoproterozoic Amdo and Jiayuqiao microblocks in the Tibetan Plateau: Implications for Rodinia reconstruction

2020 ◽  
Author(s):  
Yiming Liu ◽  
Yuhua Wang ◽  
Sanzhong Li ◽  
M. Santosh ◽  
Runhua Guo ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
South China ◽  
Tectonic Setting ◽  
Parental Magma ◽  
Tibet Plateau ◽  
Geochemical Data ◽  
The Tibetan Plateau ◽  
South China Craton ◽  
Neoproterozoic Magmatism ◽  
T Values

The Tibetan Plateau is composed of several microblocks, the tectonic affinity and paleogeographic correlations of which remain enigmatic. We investigated the Amdo and Jiayuqiao microblocks in central Tibet Plateau with a view to understand their tectonic setting and paleogeographic position within the Neoproterozoic supercontinent Rodinia. We present zircon U-Pb and Lu-Hf isotope, and whole-rock geochemical data on Neoproterozoic granitic gneisses from these microblocks. Zircon grains from the Jiayuqiao granitic gneiss yielded an age of 857 ± 9 Ma with variable εHf(t) values (−8.9 to 4.0). The Amdo granitic gneisses yielded ages of 893 ± 5 Ma, 807 ± 5 Ma, and 767 ± 11 Ma, with εHf(t) values in the range of −4.9 to 3.5. Geochemically, the granitoids belong to high-K calc-alkaline series, with the protolith derived from partial melting of ancient crustal components. The ascending parental magma of the Amdo granitoids experienced significant mantle contamination as compared to the less contaminated magmas that generated the Jiayuqiao intrusions. In contrast to the Lhasa, Himalaya, South China, and Tarim blocks, we suggest that the Amdo and Jiayuqiao microblocks probably formed a unified block during the Neoproterozoic and were located adjacent to the southwestern part of South China craton. The Neoproterozoic magmatism was probably associated with the subduction of the peripheral ocean under the South China craton and the delamination of lithospheric mantle beneath the Jiangnan orogen.

Petrogenesis of Silurian ultramafic–mafic plutons in southern Jiangxi: implications for the Wuyi–Yunkai orogen, South China

2020 ◽  
pp. 1-16
Author(s):  
Jie Yang ◽  
Wei Liu ◽  
Zuozhen Han ◽  
Zuoxun Zeng ◽  
Le Wan ◽  
...  
Keyword(s):  
South China ◽  
Lithospheric Mantle ◽  
First Episode ◽  
Jiangxi Province ◽  
South China Block ◽  
The South ◽  
Mafic Rocks ◽  
Formation And Evolution ◽  
Early Palaeozoic ◽  
T Values

Abstract The South China Block is one of the largest continental blocks located on the East Asian continent. The early Palaeozoic Wuyi–Yunkai orogen of the South China Block (known as the Caledonian orogen in Europe) is a major orogenic belt in East Asia and represents the first episode of extensive crustal reworking since Neoproterozoic time. Although this orogen is key to deciphering the formation and evolution of the South China Block, details about the orogen remain poorly defined. The Songshutang and Wushitou ultramafic–mafic units in southern Jiangxi Province, South China, have 206Pb–238U ages of c. 437 Ma, suggesting a Silurian formation age. All the Songshutang and Wushitou ultramafic–mafic rocks show relatively flat chondrite-normalized rare earth element patterns, depletions in Nb, Ta, Zr, Hf and Ti, and low ϵNd(t) values from −9.12 to −5.49 with negative zircon ϵHf(t) values from −10.84 to −2.58, resembling a typical arc magma affinity. Geochemical and isotopic data indicate that the newly identified ultramafic–mafic rocks, along with the reported Silurian mafic rocks in South China, possibly originated from the similar partial melting of an ancient subducted slab, fluid/sediment and metasomatized lithospheric mantle with varying degrees of fractional crystallization. In conjunction with other records of magmatism and metamorphism in South China, a late-orogenic extensional event led to the melting of the sub-continental lithospheric mantle in Silurian time and generated ultramafic–mafic rocks with a limited distribution along the Wuyi–Yunkai orogen and widespread late-orogenic granitic plutons in the South China Block.

scholarly journals Mesozoic Northward Subduction Along the SE Asian Continental Margin Inferred from Magmatic Records in the South China Sea

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 598 ◽  
Author(s):  
Guanqiang Cai ◽  
Zhifeng Wan ◽  
Yongjian Yao ◽  
Lifeng Zhong ◽  
Hao Zheng ◽  
...  
Keyword(s):  
South China Sea ◽  
Continental Margin ◽  
South China ◽  
Oceanic Lithosphere ◽  
The South China Sea ◽  
The South ◽  
Late Mesozoic ◽  
China Sea ◽  
Depleted Mantle ◽  
T Values

During the Mesozoic, Southeast (SE) Asia (including South China and the South China Sea (SCS)) was located in a transitional area between the Tethyan and Pacific geotectonic regimes. However, it is unclear whether geodynamic processes in the SE Asian continental margin were controlled by Tethyan or paleo-Pacific Ocean subduction. Herein, we report ~124 Ma adakitic granodiorites and Nb-enriched basalts from the Xiaozhenzhu Seamount of the SCS. Granodiorites have relatively high Sr/Y (34.7–37.0) and (La/Yb)N (13.8–15.7) ratios, as well as low Y (9.67–9.90 μg/g) and Yb (0.93–0.94 μg/g) concentrations, typical of adakites. Their Sr/Y and (La/Yb)N values coupled with their relatively low initial 87Sr/86Sr ratios (0.70541–0.70551), relatively high K2O contents (3.31–3.38 wt%), high Th/La ratios (0.33–0.40), negative εNd(t) values (−3.62 to −3.52), and their variable zircon εHf(t) values (−3.8 to +5.2) indicate that these rocks were formed by melting of subducted oceanic crust and sediments. The Nb-enriched basalts show enrichment in high field strength elements (HFSE) and have εNd(t) values of +2.90 to +2.93, as well as relatively low initial 87Sr/86Sr ratios of 0.70341–0.70343, demonstrating that they were derived from a depleted-mantle (DM) source metasomatized by silicate magmas originating from melting of a subducted oceanic lithospheric slab. By combining our findings with data from other Late Mesozoic arc-related magmatic rocks and adakites from the broader study area, we propose a geotectonic model involving subduction of young oceanic lithosphere during the Late Jurassic and northward subduction of the proto-South China Sea (PSCS) along the SE Asian continental margin during the Early Cretaceous. This conceptual model better explains the two-period Mesozoic magmatism, commonly reported for the SE Asian continental margin.

Formation Age of the Qinling Complex and the early Paleozoic Tectonic Event

2013 ◽  
Vol 734-737 ◽  
pp. 60-70
Author(s):  
Yu Shi ◽  
Xi Jun Liu ◽  
Zuo Hai Feng
Keyword(s):  
South China ◽  
North China Craton ◽  
North China ◽  
Geochemical Data ◽  
Early Paleozoic ◽  
Tectonic Event ◽  
The North ◽  
Icp Ms ◽  
South China Craton ◽  
Early Neoproterozoic

The Qinling orogenic belt (QOB) located between the North China Craton (NCC) and the South China Craton (SCC) is composed of the Northern Qinling Belt (NQB) and the Southern Qinling Belt (SQB). This study presents new geochemical data, zircon U-Pb ages and Hf isotopes from two rocks from the Qinling complex in the NQB. LA-ICP-MS zircon U-Pb dating results suggest that the Qinling complex was formed in early Neoproterozoic and experienced the early Paleozoic metamorphism. HighεHf(t) values of 9.0-12.0 for the early Paleozoic zircons indicated that there is mantle-derived magma intruding into the Qinling complex in the early Paleozoic.

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