东坪式金矿床铅同位素组成特征及其化探评价

东坪式金矿床产于华北克拉通化缘深大断裂－－尚义－赤城断裂的南侧，海西期水泉沟正长岩杂岩体内外接触带。矿体具有明显的分层笥，自上而下矿石类型由石英脉型向钾、硅化蚀变岩型过渡。矿床形成于燕山早期，成矿物质主要来源于正长岩杂岩体。矿石铅同位素组成与正长岩杂岩体相似，在＾２０７Ｐｂ／＾２０６Ｐｂ－＾２０８Ｐｂ／＾２０６Ｐｂ图解上，矿石、正长岩、矿石中的钾长石脉石及太古宇桑干群变质岩呈线性分布，矿石与正长岩

Lead isotopic compositions of the Dongping-type gold deposit and their exploration application

The Dongping-type gold deposits occur at the inner and outer contact zones of the Shuiquangou syenite complex, which locates to the south of the northern margin fault of the North China Craton. There are three types of ores in this type of deposits, pyrite-quartz vein type, pyrite - quartz - K-feldspar type, and pyrite- K -feldsparthized syenite type. The ore types vary from auriferous quartz vein at the upper part to silicified and K-feldsparthized syenite at the bottom of the ore bodies. The hydrothermal gold mineralization occurred in early Yanshanian Period, although the Shuiquangou syenite complex emplaced in Hercynian Period. The Pb, S, Si isotope and trace element investigations suggest that the principal ore forming material came from the syenite complex. The Pb isotopic compositions of the ores are similar to those of the syenite, as shown in the ~(207) Pb / ~(206)Pb -~(208)Pb / ~(206) Pb diagram, the ores, syenite, and Archean metamorphic rocks are linearly correlated and the ores are more closely related to the syenite than Archean metamorphic rocks do. Within a lateral transection profile that traversing a auriferous quartz vein, the contents of U and Th decrease as the K-feldsparthization and silicification increase, while the V_1 and V_2 have a similar variation trend with the exception of the samples near the auriferous vein. The V_1 and V_2 are pos- itively correlated to the elevation of the samples, where, hv_1 = 1 351 + 9. 3 V_1 with a correlation coefficient r = 0. 77; hv_2 = 1 222 + 17. 2 V_2, with r = 0. 92. Regarding the lead isotope data of gold deposits within the North China Craton,V_1 = -70 and V_2 = - 30 are taken as the lower limits of the Dongping-type deposits, and the maximum vertical extension of gold mineralization will be exceed 1 000 m. Thus, the gold exploration to the lower part of the gold mineralization should be reinforced in future exploration campaign.