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71.
72.
作为华南大面积低温成矿域的重要组成部分,川滇黔铅锌矿集区是我国重要的铅锌银等资源基地之一,同时该矿集区也是Ge、Cd、Ga和In等稀散元素的超常富集区域。毛坪矿床是该矿集区内第二大铅锌矿床,累计探明铅锌金属储量超过3Mt(Pb+Zn平均品位≥18%),锗(Ge)保有储量182t。本文以新发现的Ⅵ矿带(铅锌金属已探明储量≥60万t,Pb+Zn平均品位≥20%)为研究对象,利用LA-ICPMS对主要矿石矿物闪锌矿和黄铁矿进行了微区原位微量元素组成和Mapping分析。研究结果显示Ⅵ矿带闪锌矿普遍富集Ge(最高580×10^(-6),均值81.1×10^(-6))、Cd(最高3486×10^(-6),均值1613×10^(-6))和Ga(最高190×10^(-6),均值44.4×10^(-6));黄铁矿普遍富集Mn、As、Pb、Cu、Ag和Sb。与Ⅰ和Ⅱ号矿带闪锌矿相比,Ⅵ号矿带闪锌矿更富集Ge和Ga。闪锌矿中Fe和Pb以类质同象为主,偶见黄铁矿和方铅矿显微包体;Cu、Ge、Ag和As赋存形式主要为类质同象,替代方式为Ge^(4+)+2(Cu+,Ag+,As+)↔3Zn^(2+);Cd以类质同象方式赋存为主,替代机制为Cd^(2+)↔Zn^(2+);Ga和In可能主要以类质同象方式存在。黄铁矿中Pb和Mn主要以方铅矿和碳酸盐矿物显微包体为主;Cu、As和Sb以类质同象形式存在于黄铁矿中;Ag和Zn可能以独立矿物形式赋存;Co和Ni以类质同象方式替代Fe进入黄铁矿晶格中,替代方式为Ni^(2+)+Co^(2+)↔2Fe^(2+)。毛坪矿床新发现Ⅵ矿带硫化物相比典型MVT矿床硫化物具有不同的In和Ge含量以及Cd/Fe比值,结合矿床地质特征和其他证据,表明毛坪矿床成因类型特殊,有别于经典MVT铅锌矿床,属于川滇黔型铅锌矿床。 相似文献
73.
延边天宝山矿集区晚古生代岩浆-热液成矿的年代学证据——以新兴铅锌(银)矿床为例 总被引：1，自引：1，他引：0
延边天宝山矿集区已发现矽卡岩型铅锌铜矿床(立山和选厂后山)、隐爆角砾岩型铅锌(银)矿床(新兴)、沉积变质-热液改造型铜铅锌矿床(东风南山)和斑岩型钼矿床(东风北山)等四种成因类型、十余个矿床(点)。为确定矿集区内多金属成矿作用的期次,在已有工作基础上,本文首次采用LA-ICP-MS锆石U-Pb法和金属硫化物Rb-Sr法,对新兴铅锌(银)矿床开展了同位素年代学研究。结果表明,与角砾岩型铅锌(银)矿化密切相关的新兴花岗闪长岩的16个锆石测点的206Pb/238U年龄加权平均值为261. 1±3. 5Ma(MSWD=0. 46),角砾岩型矿石6件金属硫化物的Rb-Sr等时线年龄为259±3Ma(MSWD=1. 05),锶同位素初始值ISr=0. 71359,表明新兴矿床的成岩成矿时代为中二叠世晚期。结合矿集区内其它矿床的同位素测年资料分析认为,天宝山矿集区至少发生过晚古生代和早中生代两期岩浆-热液成矿事件,在中-晚二叠世形成了立山、选厂后山和新兴等多金属矿床,在早侏罗世则形成了东风北山斑岩型钼矿床。新兴矿床6件金属硫化物的Rb、Sr含量分别介于0. 1238×10-6～0. 7536×10-6和0. 3786×10-6～3. 247×10-6之间,初始Sr同位素比值(87Sr/86Sr)i介于0. 71350～0. 71371之间,均值为0. 71361,表明成矿物质以壳源为主,并有少量幔源物质的加入。综合研究表明,在中-晚二叠世(255～265Ma),受古亚洲洋俯冲作用的影响,天宝山矿集区发生了深源岩浆侵入,引发地壳物质同熔,形成富含Cu、Pb、Zn、Ag等金属元素的花岗闪长质岩浆,沿着构造裂隙上升至地壳浅部,侵位形成了矿集区内的立山、新兴、东风北山等多个晚古生代成矿(含矿)中酸性岩体。在花岗闪长岩与大理岩接触带附近,通过含矿热液交代作用,形成了立山、选厂后山等矽卡岩型铅锌铜矿床;随着岩浆期后热液在岩浆房顶部的不断聚集,挥发分的增加,当内压大于上部围岩压力时,发生隐爆作用,形成隐爆角砾岩,压力骤减引起流体不混溶,导致铅、锌、银等金属组分沉淀富集,形成新兴隐爆角砾岩型铅锌(银)矿床。 相似文献
74.
Wood debris are an important component of mangrove marine environments. Current knowledge of the ecological role of wood falls is limited by the absence of information on metazoan colonization processes over time. The aim of this study was to provide insights to their temporal dynamics of wood eukaryotic colonization from a shallow water experiment in a mangrove swamp. Combined in situ chemical monitoring and biological surveys revealed that the succession of colonizers in the mangrove swamp relates with the rapid evolution of sulfide concentration on the wood surface. Sulfide-tolerant species are among the first colonizers and dominate over several weeks when the sulfide content is at its maximum, followed by less tolerant opportunistic species when sulfide decreases. This study supports the idea that woody debris can sustain chemosynthetic symbioses over short time-scale in tropical shallow waters. 相似文献
75.
硫化物Rb-Sr同位素定年研究进展 总被引：4，自引：0，他引：4
针对金属矿床成矿年代确定混乱的问题,国内外许多矿床学家和同位素地球化学家对金属矿物常规同位素定年方法进行了有益的探索研究,尤其是对于矿石矿物以闪锌矿、方铅矿和黄铁矿为主的铅锌矿床,硫化物矿物Rb-Sr同位素定年方法显示出了其独特的优势。结合近几年开展的工作,总结国内外硫化物Rb-Sr同位素定年研究取得的成果、闪锌矿中Rb、Sr的赋存状态与定年机理以及定年适应性问题。采用闪锌矿Rb-Sr同位素组成数据拟合成等时线源自热液流体与闪锌矿之间Rb和Sr的不同分异作用,但并不是所有的闪锌矿均适合该定年技术。要成功获得年龄,需结合野外地质特征采集代表性的矿石样品,并在镜下鉴定基础上挑选合适的单矿物;在分析测试过程中,需尽可能去除次生包裹体和粘土矿物。 相似文献
76.
Komatiites and nickel sulfide ores of the Black Swan area,Yilgarn Craton,Western Australia. 2: Geology and genesis of the orebodies 总被引：1，自引：0，他引：1
S.?E.?Dowling S.?J.?BarnesEmail author R.?E.?T.?Hill J.?D.?Hicks 《Mineralium Deposita》2004,39(7):707-728
The Black Swan Ultramafic Succession hosts a number of magmatic Fe–Ni–Cu–PGE sulfide ore shoots, ranging from high grade massive ore to low grade disseminated sulfides. Of these, the most economically significant is the Silver Swan massive sulfide orebody, associated with the basal contact of the succession. The deposit varies in thickness between 5 and 20 m, reaches a N–S strike length of 75 m, extends for at least 1.2 km of vertical plunge and is open at depth. Overlying matrix (net-textured) ore is rare. Inclusions of dacite are abundant within the lower 5 m of the massive sulfide. They range from angular fragments through smooth sinuous and plumose morphologies to fine lace-like intergrowths with the sulfide matrix, and comprise variable proportions of cores of porphyritic dacite and carapaces with skeletal plagioclase phenocrysts. Dynamic crystallisation and kinetic melting textures in the carapaces indicate that the inclusions have been heated to various temperatures, some well above their liquidus temperature. The composition of the inclusions ranges from a perfect match with the immediate footwall dacites to mixtures of dacite with up to 30% komatiite. The consistent thickness of the inclusion-bearing basal layer within the massive sulphide is interpreted as the extent of 3-D physical connectivity between the inclusions and a partially molten underlying hybrid layer. Primary contacts between the Silver Swan massive sulfide orebody and overlying ultramafic rocks are marked by thin rinds containing coarse-grained chevron-textured chromites with skeletal textures. Compositions of these chromites match those from Kambalda, Perseverance and other localities, and are inconsistent with a metamorphic origin. They are interpreted as markers of primary magmatic contacts. The combination of this feature with the general paucity of matrix ore implies that the massive ore accumulated and solidified before the accumulation of the overlying thick sequence of olivine cumulates. Taken together with observations on the internal fractionation of platinum group elements within the massive ores, these observations are consistent with a model where the massive ore were emplaced at the floor of a small partially drained lava tube. The floor of the tube had been previously heated by passage of large volumes of lava, such that it had reached its melting range. The felsic inclusions within the ore are the result of buoyant ascent of partially molten substrate into the ore magma. This constitutes strong evidence for the operation of thermo-mechanical erosion during ore emplacement. The disseminated Cygnet and Black Swan orebodies show a number of distinctive features. Cygnet contains a assemblage of clasts and inclusions which are interpreted as the result of rip-up, transport and redeposition of sulfides from a pre-existing massive sulfide orebody, of which Black Duck may be a remnant. The Black Swan orebody, by contrast, does not show xenolithic features, but is characterised by an association of sulfide blebs with segregation vesicles, and by unusually coarse-grained olivine. The Black Swan orebody is interpreted as the result of transport of sulfide droplets within a lava charged with a suspended load of coarse olivine crystals.Editorial handling: Peter Lightfoot 相似文献
77.
Chusi?LiEmail author Zhanghua?Xu Sybrand?A.?de?Waal Edward?M.?Ripley Wolfgang?D.?Maier 《Mineralium Deposita》2004,39(2):159-172
The Jinchuan Ni–Cu sulfide deposit is hosted by an elongated, olivine-rich ultramafic body that is divided by subvertical strike-slip faults into three segments (central, eastern, and western). The central segment is characterized by concentric enrichments of cumulus olivine crystals and interstitial sulfides (pyrrhotite–pentlandite–chalcopyrite intergrowth), whereas the eastern and western segments are characterized by an increase of sulfides toward the lower contacts. In all segments sulfides are concentrated at the expense of intercumulus silicates. Olivine re-crystallization is found to be associated with actinolite alteration in some samples. The compositional variations of primary olivine from the sulfide-poor samples can be explained by a small degree of olivine crystallization (<5%) from a basaltic magma followed by local re-equilibration of the olivine with up to 30% trapped silicate liquid. In the sulfide-bearing samples the compositions of primary olivine record the results of olivine-sulfide Fe–Ni exchange that occurred after the trapped silicate liquid crystallized. Our olivine data indicate that Ni in the original sulfide liquids increased inward in the central segment and laterally away from the lower contact in the eastern segment. Variations in the compositions of sulfide liquids are thought to result from fractional segregation of immiscible sulfide liquid from a basaltic magma in a staging chamber instead of in situ differentiation. High concentrations of olivine crystals (mostly >50 modal%) and sulfide (averaging ~5 wt%) in the rocks are consistent with the interpretation that the Jinchuan deposit was formed by olivine- and sulfide-laden magma successively ascending through a conduit to a higher, now-eroded, level. Sulfide enrichment toward the center in the central segment and toward the lower contact in the eastern and western segments may have, in part, resulted from flow differentiation and gravitational settling during magma ascent, respectively.Editorial handling: P. Lightfoot 相似文献
78.
79.
A unique occurrence of strontian barite droplets associated with oriented planes of primary sulfide blebs in several clinopyroxene megacrysts was found in the Plio-Pleistocene basaltic tuff of Szentbékkálla (Bakony–Balaton Highland, western Hungary). The barite droplets contain 3.22–14.7 wt.% SrO, variable amount of FeO (up to 3.25 wt.%), minor CaO, CuO and NiO. Textural arrangements of oriented sulfide planes show that they were trapped as immiscible sulfide melt during crystallization of the clinopyroxene. Temperature and pressure estimation (978–1094 °C and 1.0–1.1 GPa) of the host clinopyroxenes indicate that formation of clinopyroxene megacrysts and entrapment of sulfide blebs happened under upper mantle conditions.
A genetic relationship between the sulfate and sulfide blebs is doubtful. Textural features suggest that the barite droplets might have been trapped together with the sulfide blebs from immiscible sulfide melts. However, it cannot be excluded that the barite formed during metasomatic event following the sulfide formation. 相似文献
80.
Dirk Schulze-Makuch Philip Goodell Thomas Kretzschmar John F. Kennedy 《Hydrogeology Journal》2003,11(3):401-412
Groundwater of the southern Jornada del Muerto Basin, an intermontane basin structure associated with the Rio Grande rift
located in south-central New Mexico, USA, was analyzed chemically and microbially. A microbial phospholipid fatty acids (PLFA)
analysis revealed a sparse microbial population consisting of relatively simple microorganisms with no major population changes
along the flow system. A nucleic acid (DNA) analysis of the groundwater resulted in the identification of ten eubacterial
and one archeal species. Chemical analyses revealed that sulfate along with calcium, magnesium, iron, and manganese is removed
by about an order of magnitude in concentration from the recharge area to the discharge area. The removal of iron, manganese,
magnesium, and to some extent calcium can be explained by oxidation reactions and the precipitation of dolomite. Sulfate and
additional calcium are most likely removed by the precipitation of gypsum. Thiobacillus spp. are oxidizing metal sulfides that occur as subsurface sulfide mineral deposits to sulfuric acid, which subsequently
reacts with calcium carbonate and water to precipitate gypsum. The presence of these sulfide deposits exposed to oxygenated
water in the deep groundwater flow system significantly alters its chemical and bacteriological composition.
Electronic Publication 相似文献