Geochronology, Geochemistry and Geological Significance of Late Carboniferous-Early Permian Granites in Kumishi Area, Xinjiang
详细信息
- 责任者：Chen Chao (Faculty of Earth Resources ; China University of Geosciences ; Wuhan 430074 ; China) ; Lü Xinbiao
- 刊名：Earth Science
- 出版年：2013
- 卷期：38(2)
- 关键词：花岗岩 ; granite ; 新疆 ; Xinjiang
- 页码：p.218-232
- 图表：illus., 4 tables, 44 refs.
- 分类号：0801
- issnNo：ISSN1000-2383
- isbnNo：CN42-1233/P
摘要
Granitoids are widely distributed in east part of south Tianshan orogen, forming a NWW orientated granite belt along Kumishi fault. Zhongbao and Sangshuyuanzi skarn-type tungsten deposits have been discovered in this region and the mineralization is closely related to two-mica granites. LA-ICP-MS U-Pb zircon dating yields the ages of Zhongbao and Sangshuyuanzi granites of 296±4 Ma and 293±3 Ma, respectively, which belong to Late Carboniferous-Early Permian. Both of the granites are peraluminous (A/CNK=1.11-1.48, 1.05-1.11) with high contents of SiO2 (72.51%-74.84%, 70.68%-74.14%) and primary muscovites ,which show the characteristics of syn-collision S-type granites. The samples are characterized with enriched LILE, LREE and loss of HFSE, with HREE showing moderate negative Eu anomalies. ISr values of two granites range from 0.707 6 to 0.708 8 and 0.706 5 to 0.707 7; εNd(t) values range from -6.3 to-7.1 and -4.7 to -5.1; Nd single-stage modle ages (TDM) range from 1.59 to 1.8 Ga and 1.50 to 1.56 Ga , and the old inherited zircon ages range from 2.5 to 0.8 Ga. The above data indicate that the two granites are derived from partial melting of metapelites of Xingxingxia group and might contain mix greywacke ingredients, suggesting that there exists Precambrian basement in the eastern part of South Tianshan. Based on this research and previous studies as well , we are convinced that South Tianshan ocean finally closed in Late Carboniferous-Early Permian and the appearance of A-type granites and mafic magmatism means that the south Tianshan orogenic belt enters the post-orogenic stage .Tungsten-rich Xingxingxia Group is the possible source of regional tungsten mineralization and the conversion stage from syn-collision to post-collision is the advantageous matallotecttonic system. Xingxingxia Group that had experienced the polycycle tectonism remelted again in orogenic processes in Early Permian, resulting in the final concentration of ore-forming elements.