西南三江义敦岛弧南端地壳抬升历史及资源评价意义  

The Crustal Uplift History of the Southern Tip of Yidun Island Arc in Southwest Sanjiang Region and Significance of Resource Evaluation

作　　者：刘学龙[1] 李文昌[1,2] 张娜[1] 

机构地区：[1]昆明理工大学,昆明650093 [2]云南省地质调查局,昆明650051

出　　处：《地质学报》2015年第2期289-304,共16页Acta Geologica Sinica

基　　金：中国博士后科学基金项目(2014M552547XB);云南省香格里拉县格咱地区铜多金属矿整装勘查区关键基础地质研究项目(12120114013701);云南省科技领军人才培养计划项目(2013HA001)项目联合资助的成果

摘　　要：云南格咱岛弧成矿带是西南＂三江＂（怒江、澜沧江、金沙江）多岛弧盆系中一个重要的地质构造单元,位于甘孜—理塘结合带西侧德格—中甸陆块的东缘,印支期义敦岛弧带南端。它始于晚三叠世甘孜—理塘洋壳的向西俯冲,燕山期经历了陆内汇聚和造山后伸展作用阶段,喜山期受青藏高原碰撞隆起效应的影响,本区表现为强烈的逆冲-推覆构造和大规模走滑平移活动。区内岩浆活动强烈,成矿地质条件优越,是近年来新发现的重要铜多金属成矿带,其中以印支期产出于普朗复式岩体的斑岩型铜矿床最为典型。本文通过格咱岛弧岩浆岩带主要成矿斑岩体的磷灰石裂变径迹热年代学的研究表明,裂变径迹年龄分布于12~68Ma,均小于成岩成矿时代,区内主要成矿斑岩体的剥蚀速率为0.046~0.236mm/a,剥蚀程度约为1473~2904m。通过岩体的剥蚀程度与铜多金属矿床的形成深度来分析,各成矿岩体的剥蚀深度基本上小于侵位深度,这对矿床形成后的保存情况较为有利。根据区内主要斑岩型矿床剥蚀资源量的定量计算,将矿床剥蚀情况划分为3个数量级：I级为矿床轻度剥蚀、Ⅱ级为矿床中等剥蚀、Ⅲ级为矿床严重剥蚀,为该区斑岩成矿系统资源潜力评价和深部找矿提供了理论依据。Geza island arc belt is one of the important tectonic units in the archipelagic arc-basin system in the Sanjiang area（Jiasha River,Nujiang River,Lancang River）,which is located in the eastern edge of the Dege-Zhongdian continental blocks Ganze-Litang and the southern of Yidun ia land arc.It began at GanzeLitang oceanic crust westward subduction in the Late Triassic,experienced intracontinental convergence and post-orogenic extensional phase in Yanshanian,and shows a strong thrust-nappe structure and largescale strike-slip translation activities by the effect of the collision uplift of the Qinghai-Tibet Plateau in the Himalayan.In this area,there were strong magmatic activities,superior metallogenic geological conditions,the rich mineralization and a lot of deposits.It was a newly discovered copper polymetallic ore concentration area of China in recent years,in which the porphyry copper deposits in the pulang complex is a typical representative of Indosinian porphyry copper deposits.Through the study of apatite fission track,geochronology of the major mineralized porphyry indicates that fission track age distribution in 12~68Ma and less than the age of diagenesis and mineralization,the denudation rate of the major porphyry mineralization is 0.046~0.236mm/a,denudation is about 1473~2904m.The comparative studies of emplacement depth and denudation degree show that erosion depth of the ore-forming rocks was basically less than emplacement depth,which was more favorable to the preservation of deposit after it formed.According to the quantitative calculation of erosion amount of resources to mainly porphyry deposits,the denudation was divided into three orders of magnitude：Grade I for mild denudation of deposit,GradeⅡ for medium denudation of deposit,Grade Ⅲ for severe denudation of deposit,which provides the theory basises for evaluation of the metallogenic potential and deep prospecting of porphyry metallogenic system.

关 键 词：斑岩型铜矿 斑岩体隆升与剥蚀 矿床变化与保存 印支期 格咱岛弧 三江地区 

分 类 号：P542[天文地球—构造地质学] P611[天文地球—地质学]