首页 | 官方网站   微博 | 高级检索  
     

中国大陆环境斑岩型矿床:基本地质特征、岩浆热液系统和成矿概念模型
引用本文:侯增谦,杨志明.中国大陆环境斑岩型矿床:基本地质特征、岩浆热液系统和成矿概念模型[J].地质学报,2009,83(12):1779-1817.
作者姓名:侯增谦  杨志明
作者单位:中国地质科学院地质研究所,北京,100037
基金项目:国家自然科学重点基金,杰出青年基金,国家科技支撑计划项目,地质调查项目(编号 1212010818096)资助的成果 
摘    要:中国大陆环境斑岩型矿床包括斑岩型Cu(-Mo、-Au)、斑岩型Mo、斑岩型Au和斑岩型Pb-Zn等矿床类型,主要产出于青藏高原大陆碰撞带、东秦岭大陆碰撞带和中国东中部燕山期陆内环境,在地球动力学背景、深部作用过程、岩浆起源演化、流体与金属来源等方面与岩浆弧环境斑岩型矿床存在重要差异.在大洋板块俯冲形成的岩浆弧,主要发育斑岩Cu-Au矿床或富金斑岩Cu矿(岛弧)和斑岩Cu-Mo及斑岩Mo矿床(陆缘弧).相比,在大陆碰撞带,晚碰撞构造转换环境发育斑岩Cu、Cu-Mo和Cu-Au矿床,矿床受斜交碰撞带的走滑断裂系统控制,后碰撞地壳伸展环境则主要发育斑岩Cu-Mo矿床,矿床受垂直于碰撞带的正断层系统控制;在陆内造山环境,早期发育斑岩Cu-Au矿床,晚期发育斑岩Pb-Zn矿床,它们主要沿古老的但再活化的岩石圈不连续带分布,受网格状断裂系统控制;在后造山(或非造山)伸展环境,则大量发育斑岩Mo矿和斑岩Au矿,它们则主要围绕大陆基底-克拉通(或地块)边缘分布,受再活化的岩石圈不连续带控制.大陆环境斑岩Cu(-Mo,-Au)矿床的含矿斑岩多为高钾钙碱性和钾玄质,以高钾为特征,显示埃达克岩地球化学特性.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.上地幔通过三种可能的方式向岩浆系统供给金属Cu(和Au):①提供大批量的幔源岩浆并底垫于加厚下地壳底部,构成含Cu岩浆的源岩;②提供小批量的软流圈熔体交代和改造下地壳,并诱发其熔融;③与拆沉的下地壳岩浆熔体发生反应.大陆环境含Mo岩浆系统高SiO_2、高K_2O,岩相以花岗斑岩为主,花岗闪长斑岩次之,既不同于Climax型,又有别于石英二长斑岩型Mo矿床,岩浆起源于古老的下地壳.金属Mo主要为就地熔出,部分萃取于上部地壳.大陆环境含Pb-Zn花岗斑岩多属铝过饱和型,与S型花岗岩相当,以高δ~(18)O(>10‰)和高放射性Pb为特征,Sr-Nd-Pb同位素组成反映其来源于中下地壳的深熔作用,金属Pb-Zn主要来源于深融的壳层.大陆环境含Au岩浆系统以富B花岗闪长斑岩为主,常与矿前闪长岩密切共生.Sr-Nd-Pb同位素显示,含Au岩浆主要来源于上部地壳,但曾与幔源岩浆发生相互作用.金属Au部分来源于上地壳,部分来源于地幔岩浆.大陆环境斑岩型矿床显示各具特色的蚀变类型和蚀变分带,其中,斑岩型Cu(-Mo,-Au)矿热液蚀变遵循Lowell and Guilbert模式;斑岩型Mo矿主要发育钙硅酸盐化、钾硅酸盐化和石英-绢云母化;斑岩型Pb-Zn矿主要发育绿泥石-绢云母化和绢云母-碳酸盐化,缺乏钾硅酸盐化;斑岩型Au矿强烈发育中度泥化.斑岩型矿床的成矿流体初始为高温、高fO_2、高S、富金属的岩浆水,由浅成侵位的长英质岩浆房在应力松弛环境下出溶而来,晚期有天水不同程度地混入.Cu、Mo、Pb-Zn通常沉淀于流体分相和流体沸腾过程中,而Au则主要沉淀于岩浆-热液过渡阶段.

关 键 词:斑岩矿床  含矿斑岩  岩浆起源  动力学机制  成矿模型  大陆环境
收稿时间:2009/8/12 0:00:00
修稿时间:2009/10/17 0:00:00

Porphyry Deposits in Continental Settings of China: Geological Characteristics,Magmatic Hydrothermal System,and Metallogenic Model
HOU Zengqian,and YANG Zhiming.Porphyry Deposits in Continental Settings of China: Geological Characteristics,Magmatic Hydrothermal System,and Metallogenic Model[J].Acta Geologica Sinica,2009,83(12):1779-1817.
Authors:HOU Zengqian  and YANG Zhiming
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, including porphyry Cu-Au and gold-rich porphyry Cu deposits which usually distributed in island arc setting, while porphyry Cu-Mo, Mo deposits in continental arc settings. This paper reviews some significant porphyry Cu deposits in China, unrelated subduction, including porphyry Cu(-Mo,-Au), Mo, Au, Pb-Zn deposits, mainly distributed in Tibet, Qinling collisional orogen belts, and Yanshanian intracontinental settings in Eastern China. These porphyry deposits show many differences from those which are formed in magmatic arc settings, such as geodynamic settings, tectonic control, magma source, and ore-forming fluid system. Porphyry Cu, Cu-Mo, Cu-Au deposits formed in late-collisional periods are controlled by strike-slip fault system; Porphyry Cu-Mo deposits occurred in post-collisional periods are controlled by orogen-transverse normal faults and their intersection with other faults; the ore types in intracontinental orogenic settings maybe Cu-Au early, and Pb-Zn later, deposits are mainly controlled by the grid fault system and distribute along the re-activated lithospheric discontinuous belts; while porphyry Mo, Au deposits formed in anonogenic settings mainly distribute around the continental basement-craton(or land) margin, controlled by re-activation of lithospheric discontinuous belts. These porphyry Cu(-Mo,-Au) deposits are usually associated with high-K calc-alkaline and shoshonitic magmas which are not related to oceanic-slab subduction processes. The main host rocks show geochemical affinity of adakites. The Cu(-Mo,-Au) bearing magmas were most likely derived from thickened mafic lower-crust, involving various components of juvenile mantle or delamination lower-crust. The upwelling of asthenospheric mantle to heat the juvenile lower-crust or the delamination of a thickened high-density mafic lower-crust are regarded as the major deep lithospheric processes for generating adakitic Cu magmas in continental settings. The main host rocks of the porphyry Mo deposits are granitic and granodioritic porphyry, which are characterized by high SiO_2, high K_2O contents. These Mo-bearing magmas were most likely derived from the lower crust source, distinguishing them from Climax or quartz-monzonite porphyry type. The granitic porphyry in porphyry Pb-Zn deposits are characterized by Al-supersaturated, high δ~(18)O(>10‰)and radioactive Pb, similarly as S-granite. Sr-Nd-Pb isotopes of the intrusion show that they may be formed by the middle or lower crust remelting. The main host rocks of the porphyry Mo deposits are B-rich granodioritic porphyry, which usually associated with pre-ore dioritic porphyry. Sr-Nd-Pb isotope characteristics show that the Au-bearing magma may generate partly from upper crust, and partly from mantle. In addition, the hydrothermal alteration systems of the porphyry deposits formed in continental settings show different characteristics. For example, porphyry Cu (-Mo,-Au) deposits are follow the model summarized by Lowell and Guilbert; Porphyry Mo deposits developed Ca-silicate, K-silicate and quartz-sericite alteration; intermediate argillic is the typical feature of porphyry Au deposits; however, chlorite-sericite and sericite-carbonate alteration, lack of K-silicate is the characteristics of the alteration zonation of porphyry Pb-Zn deposits. Alteration and mineralization generated by magmatic fluids which have high temperature, high fO_2, high S and metal, with meteoric component in varying degrees at late mineralization stage. The fluids exsolve at the shallow emplacement of felsic magma chamber in the stress-relaxation environment. Cu, Mo, Pb-Zn precipitate at flow distribution phase and boiling process, while Au mainly in the magmatic - hydrothermal transition stage.
Keywords:porphyry deposits  ore-bearing porphyritic rock  magmatic origin  geodynamic setting  Metallogenic model  continental environment  China
本文献已被 万方数据 等数据库收录!
点击此处可从《地质学报》浏览原始摘要信息
点击此处可从《地质学报》下载全文
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号