型锌-铅-银矿床课件

1、Zn-Pb-Ag ores in Clastic-Dominated Sediments (SEDEX)SEDEX型锌-铅-银矿床 Most in Passive Margin sequences, a few in marine-filled continental back arc or rift basins大多数发育在被动大陆边缘，少量分布在充满海水的大陆弧后或裂陷盆地中Genesis, Attrition and Life Cycle of Passive Margins被动大陆边缘的形成、消减和活动旋回Evaporative Factories:Passive margins an

2、docean closure basins蒸发岩的生产工厂：被动陆缘和大洋闭合盆地 Wilson Cycle of Ocean Basins大洋盆地的威尔逊旋回Transitional tectonic example of passive marginBack Arc basin被动大陆边缘的铅锌矿远离活动板块边缘。火山活动较弱。例子：美国东海岸大陆边缘深海扇浊积岩深海平原洋壳大陆坡大陆隆大陆架水下峡谷陆架边缘大陆壳离散边缘（初始裂谷）的高角度正断层巨厚沉积物泥砂碳酸盐和硅质软泥N. America CratonRed DogAlaskaExample of Passive Margin C

3、D formed by sub-seafloor replacement processes 被动大陆边缘典型实例，经海底交代作用形成Fate of passive margins to be involved in plate collisions-complex tectonic and post ore deformation 被动大陆边缘会经历板块碰撞、复杂的构造及成矿后形变Red Dog: Cold methane seep on Carboniferous sea floor, barite and carbonate turbidites replaced by Zn-Pb ev

4、ent, buried to 12 km in Cretaceous and silicified 红狗矿床：石炭纪海底有低温甲烷渗出体；重晶石和碳酸盐浊流沉积岩被Zn-Pb交代，随后在白垩纪被深埋12km，并被硅化。Red Dog Deposit: Worlds Largest Zn DepositSub-seafloor replacement红狗：世界最大的锌矿床海底深部的交代作用Ore fluid compositions 矿石流体成分Frequency13.918.6012345670-2-4-6-8-10-12-14-1614-19 wt. % NaCl eqv.050010001

5、500050010001500Cl/BrNa/BrSeawaterGYPNaClMgSO4K saltsTemperatureWt. % NaCl eqv.Cl/Br: seawater compositionCl/Br比值：海水成分特征RED DOG ORE FLUIDSCarboniferous Basin Configuration 石炭纪盆地形态50 Miles.+vvvvvv OceanHighlandsTidalShallow Marine Shallow Water Platform CarbonatesOld Crustal Block Angayucham OceanOld

6、Crustal BlockN FaultRed DogAnoxic or dysoxicshalesOxic/Anoxic chert/shales高地潮汐区浅海浅水台地碳酸盐缺氧页岩老地壳块体洋断层Why are some passive margins fertile and others not?为什么一些被动陆缘富集而其他的却不富集？Reflux ofcoastal brines沿岸卤水的回流Jones et al., 2002Leach et al., 2005; 2010From Kelley and Jennings (2004)Age = 338 +/- 5 MaSNQanai

7、yaqMainAqqalukPaalaaqFully lithified black muds Relatively oxidized brines with Fe, Pb, and ZnSeawaterStage 3: Deposition of barite and RBS in veins and replacement of barite第三阶段：重晶石和红棕色闪锌矿在脉中沉积；重晶石被交代。Thermal alteration of mudstone produces methane;hydrofracturing and vein formation occurs海水完全成岩的黑泥

8、泥岩的热交代产生甲烷；发生水动力破裂；脉体形成相对氧化的盐水，含Fe, Pb, ZnEWMSMassive sulfide ore 块状硫化物矿石3 cmMassive early barite + early sulfide replacement块状矿石中早期重晶石+早期硫化物交代作用200 minterstitialYellow brown sphalerite (YBS) volumetrically most significant (Main stage ore) 黄棕色闪锌矿最多（主成矿阶段矿石）Avg d34S of 3.3 = TSR of seawater sulfate

9、in pore water or pre-existing barite 平均d34S 3.3 = 空隙水或已存在的重晶石中海水硫酸盐的热化学还原是矿石中硫的主要来源Higher Fe (4%); lower Mn ( 30% salinity: Dynamic brine source! 矿质流体：盐度30%，动态卤水源区Temp 150 to 200C ? 温度：150200?Concentrated source of sulfur: barite 硫已经富集：重晶石Organic matter abundant: reductant for sulfate (seawater and

10、barite) and preservation of ore 富有机质：硫酸盐(海水及重晶石)的还原剂，有利于矿石的保留Oxidized clastic aquifer 氧化的碎屑岩含水层Focused into confined carbonate turbidites 集中在封闭的碳酸盐质浊沉岩中Long lived fluid system 长期活动的流体体系Silicification and upgrading 硅化及品位提高Zn-Pb CD Deposits in Marine-Filled Continental Back Arc Basins of North Austral

11、ia and the Sullivan Deposit in the Belt-Purcell Basin, North America澳大利亚北部海水覆盖的大陆弧后盆地中SEDEX型锌铅矿床和北美Belt-Purcell盆地中的Sullivan矿床+ Passive margin environment in marine-filled continental back arc basinMt IsaHYCCenturyCentury Mine, North AustraliaConventional Interpretation: Rift-Sag basins 通常的解释：裂陷盆地New

12、 interpretations: Passive margin environments of marine-filled continental back arc basins 新的解释：海水覆盖的大陆弧后盆地中被动边缘环境In Large et al., 2005McArthur BasinKorsch et al., 2011Nuna break-up: North Australian Basin systemNuna超大陆裂解：澳大利亚北部盆地体系Courtesy P SouthgatePlatform faciesBasinal faciesHilton-George Fishe

13、rMt Isa-typeBroken Hill-typeDominantly deep water turbiditesVery minor carbonateMainly shallow water or sub-areal environmentAbundant carbonateFrom Southgate, et al., 2013Passive margin sequence of “back arc basin”. Closure and metamorphism during Isan Orogeny ca. 1640 Ma主要为深海环境的浊积岩，只有非常少量的碳酸盐岩主要为浅海

14、环境，出现大量的碳酸盐岩“弧后盆地”中被动 边缘层序Major Fault Control on Fluid Flow Tawallah Group010 kmto BorroloolaEmu Fault ZoneHYCCalvert FaultHot Springs FaultTawallah Fault13600E1630SBatten TroughFrom Large, 2006Current Model for Century(from Broadbent et al., 2002)From Ross Large et al., 2005A model for McArthur Riv

15、er一个McArthur河矿床的成矿模型Active deformation formed flower structure that was accompanied by syn-ore deformation coeval folding of ores and sedimentary breccias构造变形形成花状构造，伴随矿体形变，同时导致矿石沉积角砾的褶皱McArthur River formed in pull-apart basin associated with strike-slip Emu fault system active during break-up of Nu

16、na SupercontinentMcArthur River矿床形成于Nuna超大陆裂解中形成的Emu走滑断裂体系所导致的拉分盆地中Mineralisation largely diageneticMetals (Cooke et al., 2001) and hydrocarbons (Williford et al., 2009) derived from upper Tawallah Group金属和碳氢化合物来源于Tawallah组Mineralisation distal expression of 1640 Ma Liebig Orogeny成矿远离造山运动From Huston

17、, 2010 .au/titles/shaping-a-nationSullivan hot reduced sediment-fill, fluid can be acidic set apart from typical CDs Sullivan矿床-充填热的还原性沉积物，酸性流体，与典型的CD矿床不同 Also see John Lydon GSC WebLydon, 2007Belt-Purcell Basin: Thick reduced rift sequence and more oxidized upper sequence: high heat flowBelt-Purcel

18、l盆地：厚的还原性裂谷地层层序和更氧化的上部层序：高热流值 Sullivan Mine cross section Sullivan矿床剖面排水口建造成层的矿石白云母（绢云母）绿泥石-钠长石-黄铁矿-(方解石)绿泥石-雌黄铁矿电气石致密块状矿石辉长岩和“花斑岩”辉长岩岩墙和岩床岩枝未蚀变的沉积岩Sullivan Mine, British Columbia, CanadaSullivan矿床，British Columbia省，加拿大闪锌矿和磁黄铁矿互层的闪锌矿和泥质岩泥质岩Lydon, 2007Northeastern margin of the Purcell basin in Fort Steele and Aldridge Times (Hy, 1983)Fort Steele 和Aldridge Times地区Purcell 盆地的北东边界Exploration for CD DepositsSEDEX矿床的勘查Passive margins from Bradley, 2008Permissive Belts: evaporites, carbonates, passive margins in evaporative belts, rich in O