| 斑岩Cu-Mo-Au矿床:新认识与新进展 |
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| 引用本文： | 侯增谦.斑岩Cu-Mo-Au矿床:新认识与新进展[J].地学前缘,2004,11(1):131-144. |
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| 作者姓名： | 侯增谦 |
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| 作者单位： | 中国地质科学院,矿产资源研究所,北京,100037 |
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| 基金项目： | 国家重点基础研究发展规划 ( 973 )项目( 2 0 0 2CB412 60 0 )，国家自然科学基金重点项目 ( 4 0 2 3 40 5 1) |
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| 摘 要： | 斑岩型矿床作为一种最重要的铜钼和铜金矿床类型一直得到人们的普遍重视 ,近些年来又取得了重要研究进展 ,主要体现在 5个方面 :①岛弧和陆缘弧是斑岩型矿床产出的重要环境 ,但大陆碰撞造山带也具有产出斑岩型矿床的巨大潜力。按矿床产出的构造环境 ,可以分为弧造山型斑岩矿床和碰撞造山型斑岩矿床 ;②弧造山型含矿斑岩主要为钙碱性和高钾钙碱性 ,而碰撞造山型含矿斑岩则主要为高钾钙碱性和橄榄安粗质 (shoshonitic)。两种环境的含矿斑岩多具有埃达克岩 (adakite)岩浆亲合性 ,但前者主要来源于俯冲的大洋板片 ,后者主要来源于碰撞加厚的下地壳。大洋板片的部分熔融缘于俯冲角度的平缓化 ,而加厚下地壳的熔融起因于俯冲大陆板片的断离 (slabbreakoff) ;③在弧造山环境 ,大洋俯冲板片的膝折 (kink)或撕裂 (slabtear)不仅导致俯冲角度变缓 ,而且引起弧地壳耦合变形 ,产生切弧断裂 ,控制斑岩铜系统的时空分布。俯冲板片撕裂引发软流圈上涌 ,诱发大洋板片熔融 ,产生含矿岩浆 ;④在碰撞造山环境 ,大陆俯冲板片的裂离导致软流圈上涌 ,向下地壳注入新生物质 ,并诱发下地壳物质熔融 ,产生含矿岩浆。碰撞后地壳伸展形成横切碰撞带的正断层系统 ,为斑岩侵位提供运移通道 ,并导致岩浆流体大量分凝和铜钼金淀积。不论
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| 关 键 词： | 斑岩型矿床 埃达克岩 成矿叠加 构造控制 成矿环境 |
| 文章编号： | 1005-2321(2004)01-0131-14 |
| 修稿时间： | 2004年3月4日 |
PORPHYRY Cu-Mo-Au DEPOSITS:SOME NEW INSIGHTS AND ADVANCES |
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| HOU Zeng-qian.PORPHYRY Cu-Mo-Au DEPOSITS:SOME NEW INSIGHTS AND ADVANCES[J].Earth Science Frontiers,2004,11(1):131-144. |
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| Authors: | HOU Zeng-qian |
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| Abstract: | The porphyry-type Cu-Mo-Au deposit is a significant genetic type of Cu-Mo and Cu-Au deposits,to which close attention has been paid widely. Some new advances in the research of such deposits have been achieved in recent years. These advances are based on some new insights into the geodynamic setting,the magmatic affinity of Cu porphyry,the telescoping of alteration system and the overprinting of epithermal system,and the structural control on porphyry Cu system. Many of porphyry-type deposits occur in island-arc and continental margin arc settings,however,some porphyry-type deposits also occur in collision orogenic settings,which shows that continental collision zones have significant potential for generating porphyry Cu systems. The Cu-bearing porphyries in arc settings are mainly calc-alkaline and potassic calc-alkaline,whereas the ones in collision orogen settings are dominantly potassic calc-alkaline and shoshonitic. The majority of porphyries in both two settings show magmatic affinity with adakite. The arc porphyries were derived from adakitic melt produced by partial melting of oceanic-slab due to flat subduction. The adakitic magmas in collision zones were derived from melting of thickened lower-crust,triggered by break-off of subducted continental slab. In arc settings,the kinks or the tear in the subducted slab result not only in flatting of the slab and asthenospheric upwelling,but also in the coupling deformation of the crust and the formation of transverse-arc faults,which control spatial localization of porphyry Cu systems. In collision orogens,the break-off of the subducted continental slab localizes asthenospheric upwelling,which inputs juvenile components and provides enough heat to cause the melting of thickened lower-crust. Like transverse-arc faults,the transverse-collision zone normal faults,formed by post-collisional crust extension,facilitate rapid ascent of magmas to high-levels in the overlying crust,where vapor saturation,exsolution of volatiles and Cu-Mo-Au deposition may occur. Whether in the oblique-convergence arc settings or in the collision orogenic settings,a series of large-scale strike-slip faults and associated pull-apart basins,usually developed either along magmatic arc or orthogonal to the orientation of main collision zone,are the significant conduit systems to facilitate the high-level emplacement of magmas and favor the decoupling of ore-forming fluids from ascending magmas. In many porphyry metallogenic provinces,the early-formed concentric K silicate (inner) and quartz-sericite alteration (outer) zones associated with mineralized porphyry body were usually overprinted by the later,structurally controlled advanced argillic alteration,showing the telescoping of alteration assemblages. Meantime,the early-formed porphyry-type Cu-Mo orebody was overprinted by epithermal Cu-Au mineralization,which formed either isolated,but spatially coexisted,two deposits,or a high-grade giant deposit. The telescoping and overprinting are widely regarded to be related to the regional uplift and exhumation during the syn- or post- mineralization phase. |
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| Keywords: | porphyry-type deposits adakite overprinting mineralization structural control geodynamic setting |
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