柴达木地块北缘南北沟岩体地球化学特征及成矿前景  

Geochemical Characteristics of Nanbeigou Intrusion in the Northern Margin of Qaidam Massif and Its Prospecting Potential

作　　者：姜常义[1,2] 王子玺[1] 杜玮[1] 王梦玺[1] 

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054

出　　处：《地球科学与环境学报》2015年第1期12-23,共12页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(41302070;41102045);青海省地质勘查基金项目(2012209);中央高校基本科研业务费专项资金项目(2013G1271100)

摘　　要：南北沟岩体位于柴达木地块北缘,出露面积4.5km2。岩石主要类型有淡色辉长岩、辉长岩、暗色辉长岩,各岩石类型之间多为过渡关系,局部呈侵入接触。主量元素化学组成属拉斑玄武岩系列。岩石相对富集大离子亲石元素,亏损高场强元素,明显亏损Nb、Ta。岩体原生岩浆属于高镁拉斑玄武岩(MgO质量分数为11.1%),在岩浆演化过程中遭受了一定程度中—上地壳物质的同化混染作用。岩体形成于古岛弧环境,是早古生代柴达木地块向祁连地块俯冲过程的产物。从岩浆分异程度、原生岩浆性质、同化混染等方面综合评价认为,南北沟岩体具有较好的铜镍硫化物矿床成矿潜力。Nanbeigou intrusion is located in the northern margin of Qaidam massif,and the outcrop area is 4.5km2.The intrusion is emplaced into amphibole plagiogneiss from Paleoproterozoic Dakendaban Group and amphibolite from Mesoproterozoic.It consists of pale gabbro,gabbro,melagabbro.They extend mainly gradual transition,and part shows intrusive contact.Rock alteration is strong,most of pyroxenes alter to amphibole,and part shows biotitization and chloritization;plagioclase shows saussuritization at different levels.Chemical composition of major element belongs to tholeiitic series.The rocks relatively enrich in large ion lithophile element（LILE）,deplete in high field strength element（HFSE）,and obviously deplete in Nb and Ta.The primary magma of intrusion is high Mg tholeiitic（mass fraction of MgO is 11.1%）,and is developed by the middle-upper crustal assimilation contamination in a certain extent during the magma evolution.The intrusion,which forms in ancient island arc environment,is the product ofQaidam massif subduction to Qilian massif in Early Paleozoic.According to the degree of magmatic differentiation,characteristics of primary magma and assimilation contamination,it is comprehensively concluded that Nanbeigou intrusion has good metallogenetic potentiality of CuNi sulfide deposit.

关 键 词：地球化学 成矿潜力 地壳混染 原生岩浆 构造环境 铜镍硫化物矿床 柴达木地块 

分 类 号：P588.1[天文地球—岩石学]