Lead and sulfur isotope studies of the Wulashan quartz-K feldspar and quartz vein gold deposit, southwestern Inner Mongolia, People's Republic of China
Lead and sulfur isotope studies of the Wulashan quartz-K feldspar and quartz vein gold deposit, southwestern Inner Mongolia, People's Republic of China
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DOI：
10.2113/gsecongeo.89.6.1289
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发表时间：
1994-10
期刊：
影响因子：
5.8
通讯作者：
F. Nie;A. Bjørlykke
中科院分区：
文献类型：
--
作者：
F. Nie;A. Bjørlykke
新发现的内蒙古西南部乌拉山金矿床赋存于乌拉山群太古宙变质火山-沉积层序中，被多处晚古生代花岗岩脉和岩基包围。金矿化发生在与这些侵入体有关的石英-钾长石和石英脉中。对乌拉山地区含金石英-钾长石、石英脉、角闪斜长片麻岩、硅长石-黑云母片麻岩、花岗岩体等21个含金矿物（方铅矿和黄铁矿）的硫同位素分析表明，含金流体中的硫主要来源于晚古生代花岗岩体和太古宙变质火山沉积岩的混合来源。含金矿脉的主要寄主岩之一角闪岩的铅同位素数据确定了斜率为0.1641±- 0.0003 （2Sigma）的对比线，对应年龄为9.498±- 76 Ma （2Sigma）。该铅同位素线与5个钾长石样品确定的大华北花岗岩基晚古生代花岗岩线也有重叠。含金石英钾长石和石英脉中13个方铅矿和黄铁矿样品的铅同位素数据位于角闪岩和大华北花岗岩基样品的铅同位素数据之间，构成一条混合线。各铅同位素（206pb / 204pb vs. 207pb / 204pb、206pb / 204pb vs. 208pb / 204pb）均呈线性变化趋势，大华北花岗岩基钾长石的放射性最强，乌拉山群角闪岩的放射性最强。这种趋势可能是地幔源铅与放射性花岗岩源铅混合的结果。铅同位素研究结果表明，角闪岩与大华北花岗岩基原岩具有相同或相近的初始铅同位素组成，但其mu值可能存在较大差异。角闪岩来源于2498 Ma喷发或侵入的与地幔相关的基性火成岩，而大华北花岗岩基则可能是由晚古生代（Variscan）构造事件中先前形成的火山沉积岩选择性重熔形成的。含金石英钾长石和石英脉中的铅、硫来源于太古代角闪岩和晚古生代花岗岩基。
The newly discovered Wulashan gold deposit in southwestern Inner Mongolia, People9s Republic of China, is hosted by Archean metamorphosed volcano-sedimentary sequences of the Wulashan Group and surrounded by a number of late Paleozoic granitoid dikes and a batholith. The gold mineralization occurs in quartz-K feldspar and quartz veins related to these intrusions.Sulfur isotope analyses of 21 sulfide mineral (galena and pyrite) samples from the gold-bearing quartz-K feldspar and quartz veins, hornblende-plagioclase gneiss, sillimanite-biotite gneiss, and granitoid intrusions in the Wulashan district suggest that the sulfur of the ore-bearing fluids was mainly derived from a mixing of sources from late Paleozoic granitoid intrusions and Archean metamorphosed volcano-sedimentary rocks.Lead isotope data for amphibolite, one of the major host rocks of these gold-bearing veins, define a correlation line with a slope of 0.1641 + or - 0.0003 (2Sigma ) which corresponds to an age of 9.498 + or - 76 Ma (2Sigma ). This lead isotope line also overlaps with the late Paleozoic granite line of the Dahuabei granitoid batholith defined by five K feldspar samples. Lead isotope data of 13 galena and pyrite samples from the gold-bearing quartz-K feldspar and quartz veins plot in between data for the amphibolite and Dahuabei granitoid batholith samples, and constitute a mixing line. Plots of all these lead isotope data ( 206 Pb/ 204 Pb vs. 207 Pb/ 204 Pb and 206 Pb/ 204 Pb vs. 208 Pb/ 204 Pb) display a linear trend, with K feldspar of the Dahuabei granitoid batholith at the most radiogenic end and amphibolite of the Wulashan Group at the least radiogenic end. This trend is probably a result of the mixing of mantle-derived lead with lead from a radiogenic granitoid source.The results of lead isotope studies indicate that protoliths of the amphibolite and the Dahuabei granitoid batholith have identical or similar initial lead isotope compositions but that they may possess quite different mu values. The amphibolite was derived from mantle-related mafic igneous rocks erupted or intruded at 2498 Ma, whereas the Dahuabei granitoid batholith was probably derived by selective remelting of previously formed volcano-sedimentary rocks during a late Paleozoic (Variscan) tectonic event. The lead and sulfur of the gold-bearing quartz-K feldspar and quartz veins were derived from multiple sources, including Archean amphibolite and the late Paleozoic granitoid batholith.