| 初论大陆环境斑岩铜矿 |
| |
| 引用本文： | 侯增谦,潘小菲,杨志明,曲晓明.初论大陆环境斑岩铜矿[J].现代地质,2007,21(2):332-351. |
| |
| 作者姓名： | 侯增谦 潘小菲 杨志明 曲晓明 |
| |
| 作者单位： | 1. 中国地质科学院,地质研究所,北京100037
2. 中国地质科学院,矿产资源研究所,北京100037 |
| |
| 基金项目： | 国家重点基础研究发展计划(973计划);国家自然科学基金 |
| |
| 摘 要： | 世界范围内大型—巨型斑岩铜矿多数产于岩浆弧(岛弧、陆缘弧)环境,含矿斑岩岩浆起源与大洋板块的俯冲作用有关。综合研究了与大洋板块俯冲无关、产于中国大陆环境的若干大型—巨型斑岩铜矿。研究发现,这些大陆环境的斑岩铜矿,虽然其基本地质特征与岩浆弧环境斑岩铜矿具有广泛的类似性,但其动力学背景、含矿斑岩性质、岩浆起源演化、金属富集过程及其构造控制机制却独具特色。这些大陆环境斑岩铜矿至少可产出于4类环境:晚碰撞走滑环境、后碰撞伸展环境、后造山伸展环境和非造山崩塌环境。大陆环境含矿斑岩以高钾质为特征,多具高钾钙碱性和钾玄质特征,通常显示埃达克岩地球化学亲和性。其岩浆通常起源于加厚的新生镁铁质下地壳或拆沉的古老下地壳。陆间碰撞期的地壳大规模增厚以及其后的软流圈上涌和岩石圈拆沉,是形成含矿岩浆的主导性机制。含矿岩浆的金属初始富集通常经历两阶段过程:(1)幔源物质直接供给金属阶段;(2)伴随含水、高氧逸度埃达克质岩浆演化金属富集阶段。在第一阶段,幔源物质主要通过两种形式供给金属:(1)以幔源组分为主的新生下地壳直接熔融;(2)拆沉下地壳熔融产生的埃达克质熔体与地幔岩石圈发生水/岩反应。在第二富集阶段,下地壳角闪榴辉岩熔融过程中角闪石大量分解产生富水的、高度氧化的埃达克质熔体,其分异演化使金属元素作为不相容元素得以在残浆中富集。大陆环境含矿斑岩的浅成侵位主要受大规模走滑断裂系统、切割造山带的断裂系统和基底线性断裂构造控制。与走滑断裂系统相伴发育的走滑拉分盆地、切割造山带的张性断裂与平行造山带的逆冲断裂带交汇部位以及不同方向的线性断裂构成的棋盘格子构造,常常控制斑岩岩浆—热液系统的空间定位。
|
| 关 键 词： | 斑岩铜矿 含矿斑岩 后碰撞 晚碰撞 岩浆起源 动力学机制 大陆环境 |
| 文章编号： | 1000-8527（2007）02-0332-20 |
| 收稿时间： | 2007-02-16 |
| 修稿时间： | 2007-02-162007-03-28 |
Porphyry Cu-(Mo-Au) Deposits no Related to Oceanic-Slab Subduction: Examples from Chinese Porphyry Deposits in Continental Settings |
| |
| HOU Zeng-qian,PAN Xiao-fei,YANG Zhi-ming,QU Xiao-ming.Porphyry Cu-(Mo-Au) Deposits no Related to Oceanic-Slab Subduction: Examples from Chinese Porphyry Deposits in Continental Settings[J].Geoscience——Journal of Graduate School,China University of Geosciences,2007,21(2):332-351. |
| |
| Authors: | HOU Zeng-qian PAN Xiao-fei YANG Zhi-ming QU Xiao-ming |
| |
| Institution: | 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China ; 2. Institute of Mimeral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China |
| |
| Abstract: | Most porphyry Cu deposits in the world occur in magmatic arc settings and are formed in association with calc-alkaline arc magmas related to subduction of oceanic-slab.This paper reviews some significant porphyry Cu deposits in China,including(1) the Mid-Miocene Gangdese porphyry Cu belt in Tibet,(2) the Himalayan Yulong porphyry Cu belt in east Tibet,(3) the Mid-Jurassic Dexing porphyry Cu ore-field and(4) porphyry Cu deposits in the Middle-Lower Yangtze metallogenic belt in east China(MLYMB).These porphyry Cu deposits show broad similarity with those in the worldwide arc settings in many aspects,such as mineralization style,alteration zonation,sulfide assemblage,and ore-forming fluid system.However,they occur in a variety of continental settings from intra-continental environments during the late and post-collisional periods followed continent-continent collision to intra-plate environments related to post-orogenic and anorogenic processes.They are usually associated with high-K calc-alkaline and shoshonotic magmas that are not related to oceanic-slab subduction processes.Main host porphyry phases are granodioritic(in east China) and monzogranitic(in Tibet),and show geochemical affinity with adakites.However,these host rocks are characterized by high K2O contents(1.2%~8.5%) and low εNd(t)(-10~+3),distinguishing them from adakites derived from partial melting of subducted oceanic-slab.These adakitic magmas were most likely derived from the thickened mafic lower crust source,involving various accounts of juvenile mantle components.The upwelling of asthenospheric mantle to heat the juvenile lower crust or the delamination of a thickened high-density mafic lower-crust are regarded to be major deep lithospheric processes for generating adakitc magmas in continental settings.The key factors led to adakitic magmas fertile are most likely crust/mantle interaction processes on the base of thickened lower crust in continental settings rather than oceanic-slab dehydration process for arc magmas.It seems that the fertility of continental magmas mainly depends on contribution of mantle metals to a juenvile lower-crustal source and to relevant hydrous highly-oxidized adakitic magmas generated during breakdown of amphibole in a mafic source.Extensional,transtensional,and transpressional tectonic regimes in continental settings are thought to not permit adakitic magmas to undergo the MASH processing like arc magmas,but favor the sufficiently voluminous evolved magmas ascent upwards to upper crust levels.The strike-slip faulting systems and associated pull-apart basins,orogen-transverse normal faults and their intersection with other faults,and pre-existing lineaments and structural weakness in continental settings provide optimal conditions for focused flow and emplacement,thus controlling the spatial-temporal localization of the Cu-bearing felsic stocks. |
| |
| Keywords: | porphyry Cu deposits ore-bearing porphyoic rock post-collission later collission magmatic origin geodynamic setting continental environment China |
| 本文献已被 CNKI 维普 万方数据 等数据库收录！ |
|
