| 安徽铜陵矿集区海西期喷流沉积流体系统时空结构 |
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| 引用本文：.2004.Spatial_Temporal Structures of Hercynian Exhalitive_Sedimentary Fluid System i n Tongling Ore Concentration Area, Anhui Province [J].Mineral Deposits,23(3):281~297 |
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| 基金项目:国土资源部专项研究计划“大型矿集区深部精细结构与含矿信息”(编号: 20010103) 和国家自然科学基金重点项目(批准号: 40234051) |
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| 中文摘要:铜陵矿集区是长江中下游成矿带七大矿集区之一，构造上经历了晚古 生代的陆缘裂陷、中三叠世的陆_陆碰撞和侏罗纪—白垩纪的陆内构造_岩浆活动。晚石炭世 的海底喷流沉积形成了广泛分布的块状硫化物，除部分构成块状硫化物矿床外，还为燕山期 中酸性岩浆活动形成的矽卡岩型矿床提供了部分硫和金属物质。为了查明海西期喷流沉积流 体系统及其时空展布特征，在铜陵矿集区内开展了以流体活动记录为对象的蚀变_流体填图 工作。结果显示，海西期喷流沉积流体系统不仅形成以块状硫化物为主体的喷流沉积记录， 而且在下伏岩系中遗留了区域规模的流体蚀变记录。以块状硫化物为主体的喷流沉积记录构 成3个喷流沉积旋回，在垂向上和横向上均具有成分和结构的分带性。流体蚀变记录在上部 构成顺层蚀变带，在中部构成沿断裂和裂隙充填的石英_硫化物脉体群，在下部则构成半整 合蚀变带，表明喷流沉积流体系统由下渗的海水在下部半整合蚀变带形成储集区，经高地热 异常的加热后，沿中部脉体群向上迁移，在进入顺层蚀变带后沿砂岩层向两侧扩散，最后经 同生断裂和裂隙向海底喷出。块状硫化物与蚀变岩、喷流沉积旋回及硫化物硫同位素的空间 展布特征，显示区内存在3个受基底断裂控制的NWW向延伸的流体活动域，包含6个以上的流 体储集区域，每个流体储集区域之上发育多个流体上升中心和海底喷流中心。 |
| 中文关键词:地质学 喷流沉积流体系统 块状硫化物 区域蚀变 铜陵 长江中下游成矿带 |
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| Spatial_Temporal Structures of Hercynian Exhalitive_Sedimentary Fluid System i n Tongling Ore Concentration Area, Anhui Province |
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| Abstract:Tongling area, one of the 7 ore concentration areas in the Middle_Lower Yangtze metallogenic belt of eastern China, has tectonically undergone a geological hist ory from Late Paleozoic continental rifting through Middle Triassic continent_co ntinent collision to Jurassic_Cretaceous intra_continental tectono_magmatic acti vation. The Carboniferous sedimentary_exhalative processes in the area produced widespread massive sulfides 303～321 Ma in age, which, in addition to forming so me Cu_bearing massive pyrite deposits, mainly provided considerable sulfur and m etals for skarn Cu mineralization associated with the Yanshanian felsic intrusio ns.To understand the Carboniferous submarine hydrothermal system, the authors chose about 1000 km2 in Tongling district for geological fluid mapping. The thick f ootwall sequences associated with the massive sulfide formation were widely alte red. This hydrothermal alteration is considered to reflect the large_scale hydro thermal fluid flow associated with Late Paleozoic crustal rifting and subsidence . There occurred three hydrothermal alteration types, i.e., deep_level semiconfo rmable silicification (S1), fracture_controlled quartz_sulfide alteration (S2_3), and upper_level concordant quartz_sericite_chlorite alteration (D3), thus forming distinct zones in the mapped area. Comparisons with modern geother mal systems suggest that the semiconformable silicification zone has recorded a sub_seafloor aquifer with the most productive hydrothermal fluid flow. The fract ure_controlled quartz_sulfide alteration formed transgressive zones, which likel y indicate the upflow path of high_flux fluids from the hydrothermal aquifer. Th e lateral zonation of the concordant alteration zones and its relationship with overlying massive sulfide lenses suggest the lateral flow and diffusive discharg ing of hydrothermal fluids in the permeable sandstone sequence. 3 large_ and 14 medium_small sized massive sulfide deposits as well as 23 massive sulfide ore sp ots were mapped in detail so as to reveal regional stratabound characteristics. The associated exhalite and chemical sedimentary rocks include (1) anhydrite_bar ite, (2) jasper_chert, (3) Mg_rich mudstone_pyrite shale, (4) barite lenses, (5) siderite_Fe_bearing dolomite, and (6) Mn_rich shale_mudstone, which usually com prise three sulfide_exhalite cyclic units in this district.The spatial distribution of these alteration zones and associated massive sulfid es and exhalites, together with regional variation in δ34S of hydrotherma l pyrite, suggests three NWW_extending fluid flow domains comprising several flu id domains, controlled by the basement faults and syndepositional faults. Each f luid domain appears to consist at least of two upflow zones, with estimated rang e of about 5～8 km in the mapped area. |
| keywords:geology, exhalative_sedimentary fluid system, massive sulfi des, regional alteration, Tongling, Middle_Lower Yangtze metallogenic belt |
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