长江中下游成矿带庐枞矿集区首例钨矿床成岩成矿时代及其意义  

LA-ICPMS U-Pb zircon age and molybdenite Re-Os dating of Donggushan, the first tungsten deposit found in the Luzong orefield, Middle-Lower Yangtze River Valley Metallogenic Belt.

作　　者：聂利青 周涛发[1] 范裕[1] 张千明[2] 张明[2] 汪龙虎[2] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]安徽省地质矿产勘查局327地质队,合肥230011

出　　处：《岩石学报》2016年第2期303-318,共16页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41320104003;41172086;41172084);中国地质调查局地质调查工作项目(12120114039701);安徽省国土资源科技项目(2013-k-1)联合资助

摘　　要：庐枞矿集区是长江中下游成矿带中重要的铁铜多金属成矿区之一。2014年在矿集区北部首次勘探发现了东顾山钨多金属矿床,其成矿与隐伏黑云母花岗岩体关系密切。东顾山矿床的矿床地质特征和成矿岩浆岩明显不同于该矿集区内已知的斑岩型铜金矿床和玢岩型铁矿床有关的岩浆岩。本次工作在详细野外地质工作的基础上,开展了东顾山钨多金属矿床地质特征、成矿岩体的岩石学和成岩成矿时代研究。研究表明,东顾山矿床为矽卡岩型钨多金属矿床,其锆石LA ICP-MS U-Pb定年结果为99.7±1.5Ma^99.9±1.7Ma,与钨矿化形成于同一期岩浆热液活动的辉钼矿的Re-Os定年结果为97.22±0.77Ma,成岩成矿时代相近,表明东顾山钨多金属矿床的成矿作用与东顾山岩体几乎同时形成,二者具有密切的成因联系。通过与区域成岩成矿时代的对比,本文首次提出庐枞矿集区内存在100Ma左右的成岩成矿事件,在成矿时代和矿床类型上明显区别于成矿带先存的140Ma的斑岩-矽卡岩型铜矿床和130Ma的玢岩型铁矿床,是长江中下游成矿带新的一期成矿作用产物,据此将成矿带的燕山期成矿时代范围重新确定在145~97Ma之间,说明长江中下游成矿带存在与华南中生代第三次大规模成矿作用对应的伸展地球动力背景下的成矿事件。东顾山钨多金属矿床为下一步在庐枞矿集区及区域上开展100Ma左右的钨多金属矿床找矿勘探提供了重要的线索,也为区域成岩成矿作用的动力学背景进一步深入研究提出了新的课题。The Luzong orefield is an important part of the Middle-Lower Yangtze River Valley Metallogenic Belt. Donggushan is a tungsten polymetallic deposit,the first deposit of this type to be discovered in the north of the Luzong orefield,and its geological characteristics and ore-forming magmatic rocks are very different from other known deposits in the Luzong orefield,such as the porphyritic iron and porphyry copper deposits. As the age of host-rocks and mineralization had not previously been determined,we carried out detailed geological field work as the basis for a systematic geochronological study of Donggushan. Closely related biotite granite yielded LA ICP-MS U-Pb zircon ages ranging from 99. 7 ± 1. 5Ma to 99. 9 ± 1. 7Ma. Molybdenite in the ore yielded Re-Os isotopic model ages of 97. 22 ± 0. 77 Ma,indicating the age of the deposit. Geological field evidence indicates that the deposit formed after the biotite granite,consistent with the dating result. The Early Cretaceous age of the Donggushan deposit at about 100 Ma is different from the age of porphyritic iron deposits in the basin（ ~ 130Ma）,and indicates a previously unrecognized epoch of mineralization in the Middle-Lower Yangtze River Valley Metallogenic Belt. Therefore,the ore-forming age of Middle-Lower Yangtze River Valley Metallogenic Belt range form 145 ~ 97 Ma,corresponding the third large-scale metallogeny of South China Mesozoic in extensive geodynamic background. This highlights potential for discovery of additional deposits and encourages exploration for tungsten deposits around 100 Ma old,so extending the favorable interval for exploration in the Middle-Lower Yangtze River Valley Metallogenic Belt.

关 键 词：东顾山钨多金属矿床 成矿作用 成岩成矿时代 庐枞矿集区 

分 类 号：P597.3[天文地球—地球化学] P618.67[天文地球—地质学]