陕西东沟金矿床地质地球化学特征及成因探讨

Discussion on the Geological and Geochemical Characteristics and Genesis of Donggou Gold Deposit in Shaanxi Province

摘要: 东沟金矿位于唐藏–商南断裂以南、凤镇–山阳断裂以北的中秦岭构造带，成矿条件好，找矿潜力大。通过总结矿区成矿地质特征和对不同期次侵入岩、蚀变岩、含金矿石等地质体的微量和稀土元素进行了测试分析，结果发现：1) 矿区位于由中性和酸性侵入岩构成的东江口岩体，主要有黑云母二长花岗岩和闪长岩出露，岩浆主要来自地壳；2) 东江口岩体的年龄约为223 Ma，推断矿区围岩形成于印支期，成矿时代为燕山早期；3) 矿区围岩轻稀土的分馏程度较高，重稀土分馏程度较低，重稀土元素分馏度值接近1，属于地壳重熔型花岗岩；4) 围岩的δEu = 0.67~0.90，表现为负铕异常，在配分曲线上为弱的铕谷，说明岩浆的分异程度相对较高，对成矿有利。综合分析认为，岩浆来源主要来自于地壳，也有少部分来自上地幔，经历过地壳的重熔作用，推断其成因类型为由构造控制的与燕山期中酸性侵入岩有关的岩浆热液型金矿床。

Abstract: Donggou Gold Mine is located in the Zhongqinling tectonic zone, which is distributed in southern of the Tangzang-Shangnan fault and northern of the Fengzhen-Shanyang fault, with good mine-ralization conditions and great prospecting potential. By summarizing the geological characte-ristics of mineralization in the mining area, the trace elements and rare earth elements of geo-logical bodies such as intrusive rocks, alteration rocks and gold-bearing ores in different pe-riods were tested and analyzed. The results show that: 1) The mining area is composed of neu-tral and acid intrusive rocks, mainly biotite difelds granite and diorite outcrops, and the magma mainly comes from the earth’s crust. 2) The age of the Dongjiangkou rock mass is about 223 Ma, indicating that the surrounding rock of the mining area was formed during the Indosinian pe-riod and the mineralization period was in the early Yanshan period. 3) The degree of fractiona-tion of light rare earths in the surrounding rock of the mining area is high; the degree of frac-tionation of heavy rare earths is low, and the value of fractionation degree of heavy rare earth elements is close to 1, which belongs to crustal remelted granite. 4) The δEu = 0.67~0.90 of the surrounding rock showed negative europium anomaly, and the weak europium valley on the distribution curve indicated that the degree of differentiation of magma was relatively high, which is beneficial for mineralization. Comprehensive analysis suggests that the source of mag-ma mainly comes from the earth’s crust, and a small part comes from the upper mantle, which has experienced the remelting of the earth’s crust, and it is inferred that its genesis type is tec-tonically controlled magmatic hydrothermal gold deposits related to acid intrusive rocks in the Yanshan period.