Zircon U-Pb Dating and Geochemical Characteristics of the Gneissic Granite in the Jinwozi Gold Deposit, Xinjiang and Their Geological Implications
详细信息
- 责任者：Cong Yuan (Institute of Mineral Resources ; CAGS ; Beijing 100037 ; China) ; Xiao Keyan
- 刊名：Geology and Prospecting
- 出版年：2012
- 卷期：50(4)
- 关键词：片麻状构造 ; gneissic structure ; 花岗岩 ; granite ; 新疆 ; Xinjiang
- 页码：p.790-798
- 图表：4 illus., 3 tables, 23 refs.
- 分类号：0801
- issnNo：ISSN0495-5331
- isbnNo：CN11-2043/P
摘要
The Jinwozi gold deposit is one of the important gold deposits in eastern Xinjiang.It is hosted in the volcaniclastic-sedimentary rocks of the upper Devonian Jinwozi Formation and the Jinwozi gneissic granite.Previous studies suggest that the Jinwozi gneissic granite formed at 356 ~ 392 Ma.This large time variation does not accord with the geological information that there is gneissic granite gravel in the bottom of the Jinwozi Formation.This conclusion,to some extent,limits the further study on the gold mineralization and geological background in this area.Accurate age determination of the Jinwozi gneissic granite is critical for researching gold mineralization and tectno-magmatic evolution.In this work,U-Pb dating and Hf isotope studies of zircon grains from the Jinwozi gneissic granite have been conducted by the high-precision LA-ICP-MS method.The result shows that the gneissic granite magma crystallization age is 429.1 ± 2.7Ma,in the middle Silurian.The εHf(t) values of Zircon and Hf two-stage isotope model ages are-3.5-+1.2 and 2545~3072 Ma,respectively.Geochemical data of granite demonstrates that it is rich in LILE and depleted in HFSE(Nb,Ta,Ti).A/CNK ranges from 1.13 to 1.14,which has the characteristics of high-K calc-alkaline volcanic rock series.It is thus concluded that the formation and emplacement of the Jinwozi gneissic granite are closely related to the closure of the South Tianshan ocean in the early Paleozoic and later collision of the Tarim plate with the Kazakhstan plate.