甘肃白银厂铜多金属矿田岩石地球化学特征及地质意义  

Geochemical Characteristics of Rocks from the Baiyinchang Copper Polymetallic ore field in Gansu Province and Geological Implications

作　　者：傅鹏[1] 陈守余[1,2] 赵江南[1,2] 杨兴彬[1] 高冀芸 平兰英 

机构地区：[1]中国地质大学(武汉)资源学院,湖北武汉430074 [2]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《地质与勘探》2016年第1期14-24,共11页Geology and Exploration

基　　金：国家自然科学基金(编号:41302264);中国地质调查局项目"甘肃省白银厂及外围铜多金属矿整装勘查区关键基础地质研究"(编号:12120114050101)联合资助

摘　　要：甘肃白银厂铜多金属矿田及外围是北祁连铜多金属成矿带的重要地段。本文以白银厂矿田重点勘查区为研究对象,重点讨论与成矿密切相关的火山岩岩石地球化学特征及其找矿评价意义。结果显示白银厂矿田火山岩呈明显的双峰式,酸性火山岩主要岩石类型为英安岩和流纹岩,属低钾系列;基性火山岩属钾玄岩系列。酸性火山岩具有两种截然不同的稀土元素配分模式,一种是产在折腰山-火焰山(以下简称折-火)地区的酸性火山岩,∑REE低(43.21×10-6~65.02×10-6),LREE/HREE以及(La/Yb)N较高(LREE/HREE=4.66~6.71,(La/Yb)N=3.51~7.12),在稀土配分曲线图上表现为右倾的半弧型;另一种是产在小铁山-铜厂沟(以下简称小铁-铜厂)地区的酸性火山岩,∑REE较低(62.78×10-6~104.36×10-6),LREE/HREE以及(La/Yb)N亦较低(LREE/HREE=2.03~2.82,(La/Yb)N=1.19~1.95),在稀土配分曲线图上表现为平坦型。折-火地区酸性火山岩与小铁-铜厂地区酸性火山岩相比Sr亏损较弱,高场强元素含量也相对较低。以上证据表明折-火地区酸性火山岩形成于大陆边缘弧环境,为地幔源区部分熔融的产物,而小铁-铜厂地区的酸性火山岩则形成于原始的大洋弧或演化的大洋弧,为深度较浅的地壳源物质重熔的产物,因此,两者不属于同一火山机构,具有不同的成矿属性。The Baiyinchang copper polymetallic ore field and peripherals are a major part of the North Qilian metallogenic belt of copper.Using the Baiyin exploration area as an example, this work focused on geochemical characteristics of volcanic rocks closely associated with mineralization and prospecting significance.Studies have shown that the volcanic rocks of this area have obviously bimodal of volcanic features, of which acidic volcanic rocks are primarily dacite and rhyolite, as a potassium ealc-alkaline series; while maflc volcanic rocks are sub-alkaline series.Acidic volcanic rocks in the area show two distinct RE E patterns.One was produced in the Zeyaoshan-Huoyanshan （hereinafter referred to ZH） acidic volcanic region, with low∑REE （43.21 × 10-6- 65.02× 10-6） , and high LREE/HREE and （La/Yb）^（ LREE/HREE = 4. 66 ^ 6. 71, （La/Yb）N = 3.51 ~ 7. 12）, and their REE plot shows a fight semi-arc type.The other was produced in the Xiaotieshan-Tongehanggou （hereinafter referred to XT） acidic volcanic region, with low∑REE （62.78× 10-6 N 104.36×10-6 ） , relatively low LREE / HREE and（La/Yb） n （ LREE/HREE = 2.03 - 2.82, （La/Yb） N = 1.19 ~ 1.95）, and their REE plot looks like flattened.The acid volcanic rocks in the ZH area have weak Sr deficit compared with those of the XT area,as well as less content of the high field strength elements.These lines of evidence imply that the acidic volcanic rocks of the ZH area formed at a continental margin arc, resulted from partial melting of a mantle source region,while those of the XT area formed at a young or matured ocean oceanic arc, as the product of remehing crustal material at shallow depth.Therefore, the two kinds of volcanic rocks are not rooted in the same volcanic edifice, with different mineralization attributes.

关 键 词：VMS型矿床 火山岩 地球化学特征 甘肃白银厂 

分 类 号：P618.4[天文地球—矿床学] P595[天文地球—地质学]