【作者】 刘学龙；

【导师】 李文昌；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2013， 博士

【摘要】 格咱岛弧带是西南“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段。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,物化探异常显著,成矿地质条件优越,成矿作用丰富,金属矿床众多,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。本文研究在对典型矿床形成的动力学背景、成矿机理、岩浆源区研究的基础上,利用裂变径迹法恢复格咱岛弧花岗质杂岩的隆升历史,求取岩体剥蚀程度的定量数据来研究矿床形成→变化→保存的演化规律,取得研究成果如下：1、利用岩石地球化学方法,对格咱岛弧岩浆岩带内主要成矿岩体的时空分布、岩石学特征及岩浆成因进行了系统分析和探讨。研究表明,格咱岛弧岩浆岩的时空分布具带状分布的特点；斑(玢)岩与区内火山岩具有相似的地球化学组成,说明两者具有相同或相似的岩浆源岩,斑(玢)岩属钙碱性岩石系列,具Ⅰ型花岗岩的特征；花岗岩构造环境判别揭示了该区岩浆岩主要形成于俯冲造山的构造环境,也指示其物质来源较深,一般为下地壳或上地幔,并具有壳幔混源的特点。2、在前人研究的基础上,利用LA-ICP-MS锆石U-Pb测年方法对普朗成矿斑岩体进行了较系统的成岩成矿时代的厘定和Hf同位素分析,来探讨该区岩浆岩形成的时代、岩石成因、物质源区及成岩构造环境。应用同位素地球化学方法,对格咱岛弧与斑岩成矿作用有关的典型矿床进行了铅同位素示踪研究,对成矿物质的来源进行了探讨研究。3、对格咱岛弧斑岩成矿系统进行较为全面的研究和总结,并对成矿系统的划分作出新的界定,将格咱岛弧成矿系统划分为印支期成矿亚系统和燕山期成矿亚系统。印支期主要发育了与安山岩同源的壳幔型中酸性岩浆作用,形成了斑岩型Cu矿成矿系统,燕山期伴随着同碰撞中酸性岩浆活动形成了斑岩型Mo(Cu)及热液型W(Mo)成矿系统,本区成矿系统的形成与洋壳俯冲有关,成矿物质来源为上地幔或下地壳,并具壳幔混源的特征。研究表明,格咱岛弧深部找矿具有较好的资源潜力,其中燕山期Mo多金属成矿已显现出良好的找矿前景。4、矿床形成后的变化与保存受各种地质作用的控制和影响,区域的隆升和剥蚀是控制矿床变化与保持的关键因素之一。研究利用黑云母矿物地质压力计和磷灰石裂变径迹(AFT)法恢复了格咱岛弧花岗质杂岩体的隆升演化历史,获得了岩体剥蚀程度和剥蚀速率的定量数据。磷灰石裂变径迹年龄数据及成岩成矿的同位素年龄,给出了区内主要斑岩型铜矿床含矿岩体的岩浆侵入作用与冷却过程的时限,从而限定了斑岩型铜矿成矿作用的时代与剥露历史。格咱岛弧成矿带内主要成矿斑岩体的侵位深度和剥蚀程度的对比分析表明,各成矿岩体的剥蚀深度都小于侵位深度,这对矿床形成后的保存较为有利。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三个数量级：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。更多还原

【Abstract】 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 located in the eastern edge of the Dege-Zhongdian continental blocks Ganzi-Litang and the southern of Yidun arc. It began at Ganzi-Litang oceanic crust westward subduction in the Late Triassic, experienced intracontinental convergence and post-orogenic extensional phase in Yanshanian, and showed a strong thrust-nappe structure and large-scale 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, significant geophysical and geochemical anomalies, 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 Pulang porphyry copper deposits is a typical representative of Indosinian porphyry copper deposits. This article researched on the dynamics background, metallogenic mechanism and magma source of the typical deposits formation, using the Apatite Fission Track method (AFT) restored the uplift history of granitic rocks in Geza arc and got the denudation quantitative data of intrusions to research on the evolution of deposits formation→post-ore modification→preservation, the research achievements of this thesis are:1. Using the geochemical method and analyzed the temporal and spatial distribution, discussed petrology characteristics and magma origin of main metallogenic porphyries in Geza arc magmatic belts. This study shown that magmatic rocks has the zonal distribution characteristics in the temporal and spatial. The similarities of porphyries and local acidic volcanic rocks in the geochemistry composition suggest that they both have the same or the similar magmatic source. The porphyry(porphyrite) and island-arc granite rocks have the same rock series (calc-alkaline) and genetic type (I-type granite). The tectonic discrimination shown that magmatic rocks mainly formed in the subduction orogenic tectonic environment, and indicated that the material also has a deeper source. It is generally believed that the source is lower crust or upper mantle and has a crust-mantle mixed characteristic.2. Based on the previous studies, we used the LA-ICP-MS U-Pb zircon method comprehensively redefiniteded the diagenetic age, mineralization age and Hf isotope analysis of Pulang mineralization porphyries, discussed the formation age of magmatic rocks in this area, the rock genesis, material source and tectonic environment. Applicated the isotope geochemical methods researched on the Pb isotope tracing and the source of the minerals of typical porphyry copper deposits in Geza arc.3. Our studies comprehensively summarized and researched on the porphyry metallogenic system of Geza arc, which can be divided into Indosinian epoch metallogenic subsystem and Yanshanian epoch metallogenic subsystem. The Indosinian epoch mainly developed intermediate-acidic crust-mantle magmatism homologous with the andesite and formed porphyry Cu metallogenic system; the Yanshanian epoch had syn-collision magmatic activities and led to product Porphyry Mo(Cu) and W(Mo) hydrothermal metallogenic system.4. The post-ore changing and preservation was controlled and influenced by various geological processes, but the regional up lift and denudation is the most important factors. Using the biotite mineral geobarometer and Apatite Fission Track (AFT) restored the uplift evolution of Geza arc granitic porphyries, obtained the quantitative data of rock erosion degree and denudation rate. AFT age and minerogenetic isotopic age given the time of intrusions and cooling process and limited the exhumation history of main porphyry Cu deposits. The comparative studied of emplacement depth and denudation degree shown that the ore-forming rocks erosion depth was less than the emplacement, which was more favorable to the post-ore changing and preservation of porphyry Cu deposits in Geza arc. According to the quantitative calculation of erosion resources to mainly porphyry deposits, the denudation was divided into three orders of magnitude:Grade I for deposit mild denudation, II was medium denudation, III for deposit severe denudation, which provided the theory basises for evaluation of the metallogenic potential and the deep prospecting of porphyry metallogenic system.更多还原