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K. Nicholson 《Mineralium Deposita》1990,25(2):126-131
A stratiform manganiferous horizon, up to 4 m thick but localised in aerial extent, occurs 10 km south-east of Inverness in north-east Scotland. It overlies Precambrian Grampian Group schists and is itself overlain by Middle Old Red Sandstone (Devonian) conglomerate, which elsewhere rests unconformably on the schists. The deposit was mined briefly in the early 1920s and is composed principally of fine-grained braunite with minor bustamite. Lower sections of the deposit contain cavities, infilled by late baryte, calcite and rhodochrosite, which resemble stromatactis. This horizon is underlain by a hematite-quartz layer, thought to represent a laterite formed by pre-MORS weathering of the underlying schists. The mineralogy and geochemistry of the manganese ore (enriched in Ag, As, Ba, Bi, Pb, Sb, Sr and Zn) are characteristic of a hydrothermal origin. Such an origin, when considered in conjunction with the outcrop, textures, mineralogy and stratigraphy of the deposit together with the palaeogeography of the region, can only be explained by deposition from hot-springs in a sublacustrine environment. Nearby baryte mineralisation may also have been deposited from the same geothermal system, which had the Caledonian 407 Ma Moy granitoid as heat source. The managanese ore is enriched in gold pathfinder elements and minor detrital gold has been found in the area. Gold mineralisation may therefore have also been deposited in the upper sections of this Devonian geothermal system. 相似文献
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《International Geology Review》2012,54(8):732-752
At the Justice mine, in the Ashanti goldfields of southwestern Ghana, chemical weathering of gold- bearing sulfide-rich lodes has produced a series of characteristic mineralogical and geochemical features that are diagnostic. In this type of gold mineralization, the most abundant sulfides are arsenopyrite, pyrite, pyrrhotite, and chalcopyrite with minor bornite and sphalerite. Gold occurs predominantly as native gold, spatially associated and chemically bound with arsenopyrite. Elsewhere gold-silver tellurides are present in quartz veins. During sulfide oxidation, arsenopyrite is replaced by amorphous and crystalline Fe-Mn arsenates, goethite, hematite, and arsenolite in box- and ladderwork textures. In the extremely weathered gossans exposed at surface or in exploration pits, goethite, hematite, and scorodite are present as pseudomorphs of oxidized arsenopyrite, which can be used as a visual pathfinder for gold-arsenic mineralization. As with arsenopyrite, pyrite and pyrrhotite alteration produces boxwork and ladderwork textures with the sulfide replaced by goethite, hematite, and a complex limonite. Copper sulfides and goethite replace bornite and chalcopyrite in ladder-type textures. With more intensive weathering, this assemblage is replaced by cuprite, goethite, and hematite. Gold mineralogy in the gossan is complex, with evidence of in situ precipitation of supergene gold as well as alteration of hypogene native gold. The concentration of pathfinder elements decreases in the gossan as a result of supergene leaching. Mass- balance calculations confirm that gossan production largely is in situ and, consequently, the hypogene geochemical dispersion patterns are preserved even though the proportion of many elements decreases as intensity of weathering increases. The problem remains of discriminating between auriferous and non-auriferous gossans, or those produced by pedological concentration of iron. Although mineral textures such as box-and ladderwork replacement and mineral pseudomorphs are useful field criteria, the most reliable guide for evaluation still is trace-element geochemistry. By use of multi-element discriminant analysis, gossans of different origins can be distinguished (along with their surface expression) from ironstones and barren lateritic soils. In regional reconnaissance studies, the evaluation of trace-element geochemistry as a discriminant along with field mapping may indicate gold potential of even extremely altered products of mineralization and, in so doing, provide a basis for the classification of weathered samples. 相似文献
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安徽宣城茶亭铜金矿床是近年来在长江中下游浅覆盖区之南陵—宣城中—新生代火山—沉积盆地中新发现的一个大型矿床。文章以赋矿石英闪长玢岩侵入体内发育的隐爆角砾岩为对象,通过详细的钻孔岩心观察和显微岩相学研究,确定其地质特征并探讨其与成矿的关系。根据钻孔岩心观察确定的岩石构造特征及钻孔剖面圈定的角砾岩空间分布特征,茶亭铜金矿床发育的隐爆角砾岩呈上大下小的不规则筒状体,被隐伏的石英闪长玢岩侵入体包孕。根据角砾特征以及角砾间的裂隙和胶结物特征,可将隐爆角砾岩划分为隐爆浆屑角砾岩、隐爆热液角砾岩和隐爆破裂角砾岩三类,三类隐爆角砾岩空间上有规律地分布,以隐爆浆屑角砾岩为中心向外或向上依次过渡为隐爆热液角砾岩→隐爆破裂角砾岩→石英闪长玢岩。基于隐爆角砾岩与蚀变和矿化的关系推测,岩浆—气液隐蔽爆破作用所产生的大量裂隙为后期含矿岩浆热液和大气降水热液的运移、交代、混合乃至卸载、沉淀成矿提供了有利的构造空间。茶亭铜金矿床的矿体赋存于浅成斑岩侵入体中,其围岩蚀变类型与分带,以及矿化呈细粒浸染状和细脉—网脉状等地质特征显示其与斑岩型矿床极为相似,但矿化富集部位与隐爆角砾岩筒（体） 的一致,且矿床同时发育角砾状、脉状、团块状矿化,矿脉中发育热液硬石膏甚至形成硬石膏岩等地质特征又明显不同于斑岩型矿床。因此,文章将茶亭铜金矿床确定为一个与中酸性浅成斑岩侵入体密切相关的隐爆角砾岩型矿床。 相似文献
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新疆哈密红石铜矿位于东天山大南湖-头苏泉岛弧带北段的卡拉塔格地区,为浅成低温热液脉型铜矿床。在矿床深部300m中段开展1:100原生晕地球化学剖面测量,选择Ag、Cu、Mo、Zn、As、Sb、Hg、Au、Pb、W、Ba、Bi、Sn等13种元素进行测试分析,查明与矿有关的地球化学特征,预测成矿有利地段。研究通过R型因子分析,识别Sb-Hg-As-Au前缘晕指示元素组合、Ag-Cu-Mo-Zn近矿晕指示元素组合、Ba-Bi尾晕指示元素组合,以及Se-Zn-Pb等元素共同代表岩浆期后中高温热液活动阶段,显示出该矿床具有多期、多阶段成矿的特征;依据C.B.格里戈良分带指数原理,建立（Sb×Hg）D/（Ba×Bi）D矿体定量预测指标,并结合矿化-蚀变特征,圈定1处成矿有利重点地段和1处成矿有利一般地段,分别为300m中段25线~19线成矿热液角砾岩筒的深部或周边,以及300m中段13线~7线1、6、9号脉矿（化）带的深部和周边;验证孔ZKY2101揭露了角砾岩筒深部的矿化情况,取得良好效果。 相似文献
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中酸性岩浆侵入体隐蔽爆破作用形成角砾岩体(筒)的同时于其中形成隐爆角砾岩型金矿床.侵入岩体规模一般较小,岩性主要为闪长岩类、石英(二长)斑岩类或正长岩类的中酸性岩石.角砾岩体在平面上呈近圆形或椭圆形,面积相对较小,在剖面上呈垂直地表的筒状,深部一般与中酸性侵入岩体相连.角砾的成分在浅部多为围岩角砾,往深部逐渐变为以花岗质角砾为主,胶结物主要是细岩屑和蚀变矿物.中酸性侵入体是矿床的成矿母岩,隐爆作用的发生及形成的隐爆角砾岩体(筒)是容矿构造,角砾岩体中的次级断裂是控矿构造,各因素对于此类型金矿床的形成起着重要的作用. 相似文献
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广东省新榕锰矿地质特征及成因探讨 总被引：3，自引：1，他引：3
新榕锰矿是广东省重要的锰矿床 ,主矿体产于地下岩溶空洞内 ,矿石中伴生银的平均含量达 10 0×10 -6以上。锰矿石中含有少量的脆银矿、溴角银矿、含锑银黝铜矿、银金矿、单斜绿铜锌矿、黄铁矿、磁黄铁矿及重晶石等矿物。据各类岩石、矿石的矿物成分 ,以及成矿元素、稀土元素地球化学特征等方面研究 ,认为Fe、Mn成矿物质主要来源于元古宇云开群和泥盆系桂头组中的富铁锰质岩层 (锰铝榴石片岩、含锰千枚岩 ) ,部分来源于矿区北部断裂带中的热液硫化物 ,伴生元素Ag、Pb、Zn等也来源于矿区北部断裂带的热液多金属硫化物。有机质 (微生物 )可能参与了成矿物质的风化淋滤、迁移、沉淀富集等成矿作用。地下岩溶空洞是最有利的成矿场所。锰矿的成矿期为新生代。矿床成因类型属迁积_岩溶堆积型锰矿 相似文献
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Mineralogy and geochemistry of a stratabound manganese deposit in the Tangganshan region of South China 总被引：1，自引：0，他引：1
The Tangganshan manganese ore deposit is a typical sedimentary-magmatic hydatopneumatogenic superimposed ore deposit. In this
paper this deposit is discussed in more detail from the following aspects: geology, ore mineralogy, and geochemistry. On the
basis of its occurrence, mineral assemblage, element geochemistry, isotopic geochemistry, and characteristics of organic matter
and fluid inclusions, the Tangganshan manganese ore deposit has proved to be a new-type manganese ore deposit that has been
enriched by magmatic-pneumatolic solutions. Most of the ore-forming elements were derived from the ore deposit itself, and
the rest from the magmatic-pneumatolitic solutions. 相似文献
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Specific features of the geochemistry of manganiferous siliceous rocks confined to Devonian volcanogenic complexes of the Magnitogorsk belt in the South Urals are discussed. It is shown that with respect to the distribution of the major petrogenic and rare earth elements, as well as base and rare metals, manganese rocks are comparable with rocks of the low-temperature hydrothermal sources in active volcanic zones of the World Ocean. Our results agree well with the existing concepts about the hydrothermal-sedimentary origin of manganese deposits in the South Urals and corroborate this hypothesis with new independently obtained data. 相似文献
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A metasomatic origin for the iron-oxide Au-Cu Starra orebodies, Eastern Fold Belt, Mount Isa Inlier 总被引：2，自引：0，他引：2
J. F. Rotherham 《Mineralium Deposita》1997,32(3):205-218
The Starra ironstone-hosted Au-Cu deposit in northwest Queensland, Australia, displays evidence of a polyphase history of
late-post metamorphic, structurally controlled metasomatism. The mineralisation is hosted within several massive ironstone
units which occur at a lithological contact of metamorphosed sandstone and siltstone sequences and foliated chlorite-biotite-magnetite
schists. The ironstones strike north-south and occur as discontinuous lenses that cross cut the host rocks in places. Magnetite
ironstone textures are generally massive in appearance, but relict deformed breccia and foliation textures are locally preserved.
Sulphide ore textures are more brittle and consist of fine, pervasive brecciation of the ironstones and host rocks. Petrological
and textural observations support a hydrothermal origin for both ironstone and mineralisation. Three dominant post-peak metamorphic
paragenetic stages of alteration and mineralisation are recognised: (1) early widespread Na-Ca metasomatism consisting of
albite-quartz-actinolite-scapolite, (2) localised K-Fe metasomatism consisting of biotite-magnetite-hematite- quartz-pyrite
and (3) the mineralising stage consisting of anhydrite-calcite-hematisation of magnetite-pyrite-chalcopyrite-gold and extreme
chloritisation of biotite. The Na dominant alteration occurs throughout the Eastern Fold Belt and for at least 50 km to the
east and 150 km to the north of Starra. The ironstones were products of localised Fe-metasomatism associated with shearing
and brecciation of previously Na-metasomatised host rocks. Gold and copper mineralisation resulted from the interaction of
magnetite, a late oxidising fluid and an increase in pH. This produced variable hematisation of magnetite and caused the solubility
of chloride-complexed gold to decrease dramatically. High gold:copper ratios can be explained in terms of the solubility differences
of gold and copper in the thermochemical conditions that existed at Starra.
Received: 15 May 1996 / Accepted: 17 January 1997 相似文献
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湖南桃江奥陶系磨刀溪组锰质岩的内碎屑结构和重力流沉积 总被引：2，自引：0，他引：2
湖南桃江一带的奥陶纪锰质碳酸盐岩,具有清晰的内碎屑结构和一些粒度递变沉积构造。锰质岩或锰矿层呈薄层或条带夹在含有笔石的黑色泥页岩中,表现出它们在成因或沉积环境方面的极不协调。以砂屑和藻屑为主组成的白色、灰白色锰质碳酸盐岩是清洁、浅水、碱性环境中的产物;以细粉砂级颗粒为主并含有硅质、碳质的泥页岩则是污浊、深水、酸性环境中的沉积。这种不协调的沉积组合是由于浅水锰质碳酸盐沉积物以重力流方式进入深水盆地与黑色泥质沉积物混合、交互沉积结果。 相似文献
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山东七宝山角砾岩筒成矿流体构造动力学过程 总被引：3，自引：0，他引：3
山东七宝山角砾岩筒内外流体构造（岩）类型多样,具自身特有的时空结构。岩筒内角砾岩胶结胶体中的结晶矿物和矿体类型在空间分布上具规律性的结构特征,并与角砾岩体分布的结构相吻合。角砾岩筒结构,构造的构造动力学分析结果表明,角砾岩筒岩石的破裂形成于流体的双重致裂作用的脉动扩展,即：在流体的热应力和液压双重作用下形成性质不同的节理裂隙和上凸锥面状裂隙带,并脉动式往上扩展形成圆柱状压裂角砾岩体;锥面状裂隙带顶 相似文献
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山东五莲七宝山金铜矿床地球化学特征及成因分析 总被引：8，自引：0，他引：8
七宝山金铜矿床产于鲁东胶莱坳陷西南缘，沂沐断裂带东亚带、受中生代破火山口内陷爆角砾岩筒的控制。本文较系统地论述了该矿床微量元素、同位素、流体包裹体地质地球化学特征，认为成矿与橄榄安粗岩系火山－侵入杂岩关系密切，成岩、成矿物质同源。均来自上地幔或下部地壳，矿化发生在中低温浅成条件下，属次火山中低温热液矿床。 相似文献
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