青海牛苦头地区海西期岩浆岩年代学、源区、成因及地球动力学背景  

The chronology,origin,genesis and geodynamic background of Hercynian magmatic rocks in Niukutou area,Qinghai Province

作　　者：耿健 王玉往[1] 王新雨 陈昱 Geng Jian;Wang Yuwang;Wang Xinyu;Chen Yu(Beijing Institute of Geology for Mineral Resources Co.,Ltd.,Beijing 100012;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083)

机构地区：[1]北京矿产地质研究院有限责任公司,北京100012 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质科学》2025年第1期165-190,共26页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：中国铜业青海鸿鑫矿业有限公司找矿项目“青海省格尔木牛苦头及外围铅锌成矿规律研究与潜力评价”(编号:QHHXKZZYB2020001)资助。

摘　　要：祁漫塔格铅锌多金属成矿带地处东昆仑造山带西段,是我国非常重要的成矿带。该成矿带海西期早-中泥盆世岩浆作用强烈,侵入岩复杂。本文以祁漫塔格东段牛苦头地区为研究区,分析讨论了早-中泥盆世岩浆岩特点,主要的岩浆岩岩石组合有:黑云母闪长岩、黑云母石英闪长岩、黑云母花岗闪长岩/花岗闪长岩、正长花岗岩、黑云母花岗岩,平均年龄400.7~381.6 Ma。全岩主量元素地球化学研究表明,SiO_(2)与TiO_(2)、Al_(2)O_(3)、Fe_(2)O_(3)、MgO、CaO、P_(2)O_(5)呈负相关关系;SiO_(2)与K2O呈现正相关关系。黑云母(石英)闪长岩属于准铝质钙碱性类岩石;(黑云母)花岗闪长岩和花岗岩类,属于高硅的准铝质—偏铝质钙碱性—高钾钙碱性类岩石,均表现出I型花岗岩的特征。稀土元素方面,表现出轻稀土元素相对富集,重稀土元素相对亏损,配分曲线略向右倾的特征,由中酸性到酸性的演化过程中,轻重稀土分异和铕负异常增强。微量元素方面,表现出与后碰撞环境下形成的岩浆岩类似的特征,整体为亏损高场强元素(P、Nb、Ta、Ti)和过渡元素(Sr、Ba),富集大离子亲石元素(Rb、Th、U),不同之处在于花岗岩类的高场强元素亏损更强,大离子亲石元素更富集,并且花岗岩类有较强的Sr负异常。Hf同位素研究表明,研究区岩浆岩由幔源基性岩浆与壳源花岗质岩浆发生不同程度混合作用而生成。综合该地区的构造演化背景,本文推断牛苦头地区海西期岩浆岩形成于后碰撞伸展背景,其岩浆由地幔底侵古老地壳,古老地壳发生部分熔融,导致壳源与幔源岩浆混合而形成。Qimantage lead-zinc polymetallic metallogenic belt,located in the west of East Kunlun orogenic belt,is a very important metallogenic belt in China.This metallogenic belt is characterized by strong Early and Middle Devonian magmatism and complex intrusive rocks.The characteristics of Early and Middle Devonian magmatic rocks are analyzed and discussed in the Niukutou area of the eastern Qimantage.The main magmatic rock associations are as follows:biotite diorite,biotite quartz diorite,biotite granodiorite/granodiorite,syenite granite,biotite granite,with an average age of 400.7~381.6 Ma.The geochemical study of the whole rock principal elements shows that SiO_(2) is negatively correlated with TiO_(2),Al_(2)O_(3),Fe_(2)O_(3),MgO,CaO and P_(2)O_(5).SiO_(2) and K2O show a positive correlation.Biotite(quartz)diorite belongs to quasi-aluminous calc-alkaline rocks.The granodiorites and granites,and the quasi-aluminous-quasi-aluminous-high-potassium calc-alkaline rocks belonging to high silicon,all show the characteristics of I-type granites.In terms of rare earth elements,light rare earth elements are relatively enriched,heavy rare earth elements are relatively depleted,and the partition curve is slightly to the right.During the evolution process from medium acid to acid,the differentiation of light and heavy rare earth and europium are negatively enhanced.In terms of trace elements,it shows similar characteristics to magmatic rocks formed in post-collision environments,with the overall loss of high field strength elements(P,Nb,Ta,Ti)and transition elements(Sr,Ba),and the enrichment of large ion lithophile elements(Rb,Th,U).The difference is that granites have stronger loss of high field strength elements and more enrichment of large ion lithophile elements.Besides,the granites have strong Sr negative anomaly.Hf isotope studies show that magmatic rocks in the study area are formed by different degrees of mixing between mantle-derived basic magma and crust-derived granitic magma.Based on the tectonic evolution background

关 键 词：岩浆岩 岩石组合 主微量元素 HF同位素 牛苦头地区 祁漫塔格 

分 类 号：P588.1[天文地球—岩石学] P597[天文地球—地质学]