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| SPATIAL-TEMPORAL DISTRIBUTION OF W AND Sn IN CLASTIC SEDIMENTARY ROCKS ALONG A TRANSECT ACROSS SOUTH CHINA AND ITS IMPLICATIONS |
| ZHAO Qi-chao, CHI Qing-hua, WANG Xue-qiu, LIU Dong-sheng, LIU Han-liang, ZHOU Jian |
| Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Science, Langfang 065000, China |
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Abstract South China is comprised of Yangtze and Cathaysia blocks bounded by the NEE-SWW extending Jiangshan-Shaoxing fault. In order to have a better understanding of the abundance and spatial-temporal distribution of each element in South China, the authors have conducted a geochemical investigation along a 2500 km transect in South China since 2008. 470 samples of fine-grained clastic sedimentary rocks from Middle Proterozoic to Cretaceous in age were collected from the Yangtze block to Cathaysia block at a spacing of 1 site/1~4 km. Analyses of 76 elements have provided us with an insight into the composition and distribution of major and minor elements in sedimentary rocks from Middle Proterozoic to Cretaceous. All the samples are characterized by significant fractionation of LREE and HREE and negative Eu anomalies (Eu/Eu*=0.67 on average). The significant depletion of Ca, Na and Sr and the high CIW values suggest intermediate to intense chemical weathering of the source rocks. Discrimination diagrams involving La, Th, Sc, Co, and Hf indicate a multiple lithological source composed of granitic, andesitic and felsic volcanic rocks. The geochemical features show that the samples were derived from distant and large provenances, and the concentrations of tungsten and tin of the samples can provide robust estimates of the composition of their region. Along the transect, the values of W and Sn decrease from southeast to northwest and descend abruptly near the Jiangshan-Shaoxing fault. The distribution of W and Sn matches well with the characteristics of W-Sn mineralization in the Cathaysia Block. The Cathaysia Block has high W and Sn relative to UCC, and peak values are existent in the Middle Proterozoic-Ordovician rocks, reflecting the high background in this block, which might explain the reason for the formation of the world's largest W, Sn metallogenic province.
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Received: 30 November 2013
Published: 10 April 2014
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