高校地质学报2017，Vol.23Issue(4)：591-605,15.DOI:10.16108/j.issn1006-7493.2017020
安徽宣城茶亭铜金矿床赋矿石英闪长玢岩锆石U-Pb年龄及岩石成因
Zircon U-Pb Age and Genesis of the Ore-bearing Quartz-dioritic Porphyries in the Chating Cu-Au Ore Deposit,Xuancheng City,Anhui Province
摘要
Abstract
The Chating Cu-Au deposit in the Xuancheng City of Anhui Province is a newly discovered porphyry deposit in the Middle and Lower Yangtze River Valley Metallogenic Belt(MLYB)during recent years. In this paper,we conducted zircon LA-ICP-MS U-Pb dating,major elements,trace elements (including REEs),Sr-Nd isotopes and zircon Hf isotope study on the ore-bearing quartz-dioritic porphyritic intrusive rocks from the drilling holes of the ore deposit,in order to reveal its geological and geochemical characteristics,and to discuss petrogenesis of the rocks. The zircon U-Pb age for the ore-bearing quartz-dioritic porphyry is 137.8±1.3 Ma(MSWD=0.72),suggesting that it was generated during Early Cretaceous. The ore-bearing quartz-dioritic porphyries have high contents of alkalinity,especially with Na enrichment,and can be grouped into sub-alkaline and high-K calc-alkaline series. They are enriched in light rare earth elements and large ion lithophile elements (e. g.,K,Rb,Sr,Ba),depleted in high field strength elements(e. g.,Nb,Ta,Ti),and show unconspicuous negative Eu anomalies. These rocks have(87Sr/86Sr)i ratios ranging from 0.706403 to 0.707903,show lowεNd(t)values ranging from-7.4 to-13.3,and with variable zirconεHf(t)values of-4.25～-11.75(t=137.8 Ma). Compared with the igneous rocks in other districts along the MYLB,the geochemical features and the emplacement ages of the ore-bearing rocks from the Chating Cu-Au ore deposit are quite different from those in the fault depression zone(e. g.,the Ningwu and the Luzong basins). Rather,they are much similar to those in the fault uplift zone(e. g.,the Tongling ore concentrated area). According to the above geological and geochemical characteristics,it is concluded that the magma of the ore-bearing quartz-dioritic porphyries were generated by mixing of enriched lithospheric mantle-derived magma and lower crust-derived magma. They might have experienced the same petrogenetic process as those of the Tongling ore concentrated area in the fault uplift of MYLB,that is,the magmas were originated from partial melting of enriched lithospheric mantle and the induced partial melting of lower curst. The both magmas mixed in the deep magma chamber,thus generated the parent magma of the quartz dioritic porphyries. The parent magmas may also be contaminated by upper crust materials and suffered a certain degree of fractional crystallization before emplaced in a shallow depth.关键词
岩石成因/U-Pb年龄/Sr-Nd-Hf同位素/斑岩铜金矿床/安徽宣城茶亭Key words
petrogenesis/U-Pb ages/Sr-Nd-Hf isotopes/porphyry Cu-Au deposit/Chating/Xuancheng/Anhui province分类
天文与地球科学引用本文复制引用
江峰,徐晓春,钱仕龙,王蒙,杨前国,李凯..安徽宣城茶亭铜金矿床赋矿石英闪长玢岩锆石U-Pb年龄及岩石成因[J].高校地质学报,2017,23(4):591-605,15.基金项目
国家自然科学基金(41472066) （41472066）
安徽省国土资源科技项目(2014K3)资助 （2014K3）
