Geochemistry of Miocene trachytes in Bugasi, Lhasa block, Tibetan Plateau: Mixing products between mantle- and crust-derived melts?

Chen, Jianlin; Zhao, Wenxia; Xu, Ji‐Feng; Wang, Baodi; Kang, Zhiqiang

doi:10.1016/j.gr.2011.06.008

Cited by 40 publications

(11 citation statements)

References 74 publications

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“…A shear-wave splitting study suggested that the present-day velocity gradient tensor field within the crust and mantle is correlated (Holt, 2000). These pieces of geophysical evidence, together with a geochemistry result that the Cr and Ni concentrations and Mg# are relatively high in this region (Chen et al, 2012), suggest that the high-V zone is probably a mixed product of mantle and crust materials, not only eclogitization. Considering the breakoff model and the shallower depth of the high-V zone (Hetenyi et al, 2006), we prefer that the high-V zone in the crust of the Himalaya orogen and the Lhasa terrane may reflect a mixed product of cooling mantle materials and lower crust partial eclogitization, which may explain the different mechanisms between the interrupted flow under central-southern Tibet and the wholesale extrusion under northern Tibet.…”

Section: Complex Crustal Structuresmentioning

confidence: 96%

Tomographic imaging of the underthrusting Indian slab and mantle upwelling beneath central Tibet

Zhang

Zhao

et al. 2015

Gondwana Research

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To better understand the pattern of convergence between the Indian and Eurasian plates, we determine a high-resolution P-wave tomography of the crust and upper mantle under southern to central Tibet using a large number of high-quality data collected by the ANTILOPE-II and Hi-CLIMB projects. A significant low-velocity zone is detected above the northward underthrusting Indian slab beneath the Indus-Tsangpo suture, which may reflect fault zones or (incomplete) fragmentation as well as melts and/or fluids associated with the dehydration of the underthrusting Indian slab. The variations in the diving depth and extending distance of the Indian slab, under the ANTILOPE-II and Hi-CLIMB seismic profiles, may be caused by the differences in the viscosity contrast between the Indian slab and the surrounding mantle as well as strong structural heterogeneities in the upper mantle under the study region. Both high and low velocity anomalies are revealed in the mid-to lower crust under southern Tibet, which may reflect the complex pattern of crustal structure. The

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Section: Complex Crustal Structuresmentioning

confidence: 96%

Tomographic imaging of the underthrusting Indian slab and mantle upwelling beneath central Tibet

Zhang

Zhao

et al. 2015

Gondwana Research

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“…Trace elements were measured using an ELEMENT XR ICP-MS at the Beijing Research Institute of Uranium Geology, with precision above 5%. The analytical procedure for the ICP-MS analysis is described by [34].…”

Section: Whole-rock Major and Trace Elementsmentioning

confidence: 99%

Geochronology, Oxidization State and Source of the Daocheng Batholith, Yidun Arc: Implications for Regional Metallogenesis

Zhang

Xue

2019

Minerals

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The Daocheng batholith consists of granite, granodiorite and K-feldspar megacrystic granite, which is located in the north Yidun Arc. It is a barren batholith in contrast to plutons of the same age that contain major copper deposits, such as Pulang to the south. In the Daocheng, abundant mafic microgranular enclaves (MMEs) mainly developed within granodiorite and K-feldspar megacrystic granite, which are characterized by quenched apatite, quartz eyes and plagioclase phenocrysts. LA-ICP-MS zircon U–Pb dating of host granodiorite yielded ages ranging from 223 Ma to 210 Ma, with a weighted mean of 215.3 ± 1.8 Ma. Zircons from MMEs yielded ages ranging from 218 Ma to 209 Ma, with a weighted mean of 214.2 ± 1.4 Ma. Geochemical analyses show that granodiorite is high-K, calc-alkaline and I-type, with SiO2 contents ranging from 67.90% to 70.54%. These rocks are metaluminous to marginally peraluminous (A/CNK = 0.98–1.00) and moderately rich in alkalis with K2O ranging from 3.28% to 4.59% and Na2O ranging from 3.18% to 3.20%, with low MgO (1.08%–1.29%), Cr (12.7 ppm–16.8 ppm), Ni (5.19 ppm–6.16 ppm) and Mg# (35–49). The MMEs have relatively low SiO2 contents (56.34%–60.91%), higher Al2O3 contents (16.06%–17.98%), higher MgO and FeO abundances and are metaluminous (A/CNK = 0.82–0.83). The MMEs and host granodiorite are enriched in light rare-earth elements (LREEs) relative to heavy rare-earth elements (HREEs), with slightly negative Eu anomalies, and enriched in Th, U and large ion lithophile elements (LILEs; e.g., K, Rb and Pb), and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, P and Ti), showing affinities typical of arc magmas. The zircon εHf(t) values (−6.28 to −2.33) and ancient two-stage Hf model ages of 1.92 to 1.25 Ga, indicating that the magmas are generally melts that incorporated significant portions of Precambrian crust. The relatively low silica contents and high Mg# values of the MMEs, and the linear patterns of MgO, Al2O3 and Fe2O3 with SiO2 between the MMEs and host granodiorite, showing the formation of MMEs are genetically related to magma mixing. The Daocheng granodiorite is characterized by much lower zircon Ce4+/Ce3+ (average of 3.53) and low fO2 value (average of ∆FMQ = –10.84), whereas the ore-bearing quartz monzonite porphyries in the Pulang copper deposit are characterized by much higher zircon Ce4+/Ce3+ (average of 52.10) and high fO2 value (average of ∆FMQ = 2.8), indicating the ore-bearing porphyry intrusions had much higher fO2 of magma than the ore-barren intrusions considering that the high oxygen fugacity of the magma is conducive to mineralization.

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“…The trace elements, including rare earth elements (REEs), high‐field‐strength elements (HFSEs), and large‐ion lithophile elements (LILEs), were determined by ICP–MS (Agilent 7500a) at the GIGCAS. The analytical procedure for the ICP–MS analysis is similar to that described by Chen, Zhao, Xu, Wang, and Kang (). Trace‐element concentrations were corrected using the USGS standard BCR–1.…”

Section: Analytical Methods and Resultsmentioning

confidence: 99%

Geochronology, mineralogy, and geochemistry of the Late Triassic Xiuwacu biotite granite in the southern Yidun Terrane, southwest China: Insights into the petrogenesis and magmatic fertility

et al. 2019

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The southern Yidun Terrane formed in response to the westward subduction of the Garzê-Litang oceanic lithosphere. The Xiuwacu pluton, consisting of the Late Triassic biotite granite and Late Cretaceous monzogranite porphyry, is located in the northern portion of the southern Yidun Terrane. It hosts the Late Cretaceous quartz-vein-type Mo-W deposit genetically related to the intraplate monzogranite porphyry. However, the petrogenesis and magmatic fertility of the biotite granite remain unclear. Sixteen zircons from the biotite granite yield a weighted mean 206 Pb/ 238 U age of 217 ± 1.2 Ma, indicating that the biotite granite emplaced synchronously with the arc-related andesites and porphyries in the southern Yidun Terrane. Unlike these slab melt-derived adakitic rocks, the Xiuwacu biotite granites show typical I-type granite affinities, with relatively high SiO 2 contents, low Sr/Y ratios, and high Y contents. These granites display depleted zircon Hf isotopic signatures (ƐHf(t) = 0.6-3.8) but enriched whole-rock Sr-Nd and zircon O isotopic signatures, suggesting that the mixing between juvenile materials and external enriched melts might have contributed to the generation of biotite granite. Moreover, they show relatively high Al 2 O 3 / (FeO T + MgO + TiO 2 ), Th/Yb, and Th/Nb ratios, which are collectively indicative of the input of sediment melts extracted from subducting slab into the melt source of biotite granite. The high MgO, TiO 2 , F, and Cl contents of biotite and the excess Al of plagioclase suggest that the Xiuwacu biotite granites formed under high oxygen fugacities, magmatic water contents, and volatiles components and they might have Cu prospecting potentials.

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Geochemistry of Miocene trachytes in Bugasi, Lhasa block, Tibetan Plateau: Mixing products between mantle- and crust-derived melts?

Cited by 40 publications

References 74 publications

Tomographic imaging of the underthrusting Indian slab and mantle upwelling beneath central Tibet

Tomographic imaging of the underthrusting Indian slab and mantle upwelling beneath central Tibet

Geochronology, Oxidization State and Source of the Daocheng Batholith, Yidun Arc: Implications for Regional Metallogenesis

Geochronology, mineralogy, and geochemistry of the Late Triassic Xiuwacu biotite granite in the southern Yidun Terrane, southwest China: Insights into the petrogenesis and magmatic fertility

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