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首页> 外文期刊>THE CANADIAN MINERALOGIST >MINERALS OF Au, Ag AND U IN VOLCANIC-ROCK-ASSOCIATED MASSIVE SULFIDE DEPOSITS OF THE NORTHERN APPENINE OPHIOLITE, ITALY
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MINERALS OF Au, Ag AND U IN VOLCANIC-ROCK-ASSOCIATED MASSIVE SULFIDE DEPOSITS OF THE NORTHERN APPENINE OPHIOLITE, ITALY

机译：意大利北部阿片辉石的火山岩伴生块状硫化物矿床中的Au，Ag和U矿物

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摘要

Ore samples from five copper sulfide deposits associated with Jurassic ophiolites in the Northern Apennine belt of Italy were found to contain gold, acanthite or argentite (Ag_2S), and freibergite (Ag,Cu,Fe)_(12)(Sb,As)_4S_(13). These precious-metal minerals are part of a complex assemblage of microscopic to submicroscopic (<10 mum) accessory phases, including uraninite, barite, galena, smithsonite, siderite, a La-Ce carbonate and a Sn hydroxide, attributable to the rare mineral hydroromarchite Sn_3O_2(OH)_2. The textures of the sulfide host are indicative of metal deposition in a range of conditions, involving initial precipitation from hot, metal-charged solutions (syngenesis), followed by post-depositional replacement of biological material and resedimentation of clasts, at low temperature (epigenesis). Syngenetic gold is Ag-rich and associated with uraninite in Fe-Cu-rich ore. The fineness of native gold increases by loss of Ag into secondary Ag_2S during seafioor weathering of the sulfides. Freibergite forms during recrystallization of sphalerite in massive Zn-Fe ore. Hydroromarchite occurs in massive Zn-Fe ore, closely related with late deposition of siderite and secondary pyrite, possibly due to the action of neutral to basic and reducing waters flushing through the ore in the initial stages of seafioor diagenesis. The widespread evidence for seafioor resedimentation and for biogenic-activity-driven reworking of the sulfides suggests a transition from proximal VMS to a more distal type of deposit formed by resedimentation processes in a dynamic tectonic environment. This scenario seems to be consistent with the interpretation of the Jurassic Ligurian ocean as a narrow basin in the early stage of its opening, having its modern analogue in the Red Sea.
机译：在意大利北部亚平宁带与侏罗纪蛇绿岩相关的五个硫化铜矿床的矿石样品中发现含有金，铅锌矿或闪锌矿（Ag_2S）和方铁矿（Ag，Cu，Fe）_（12）（Sb，As）_4S_ （13）。这些贵金属矿物是微观到亚微观（<10微米）辅助相的复杂组合的一部分，包括尿石，重晶石，方铅矿，新秀丽，菱铁矿，La-Ce碳酸盐和Sn氢氧化物，这归因于罕见的矿物水铬铁矿Sn_3O_2（OH）_2。硫化物基质的织构表明金属在一定条件下的沉积，包括从热的，金属带电的溶液中初始沉淀（同化），然后在低温下进行生物材料的沉积后置换和碎屑的再沉淀（表生）。 ）。同生金富含银，并且与富铁铜矿石中的铀矿有关。在硫化物的海底风化过程中，Ag损失进入次生Ag_2S中，从而增加了天然金的纯度。在块状Zn-Fe矿石中闪锌矿重结晶过程中会形成贝氏体。水铁锰矿发生在块状Zn-Fe矿石中，与菱铁矿和次生黄铁矿的后期沉积密切相关，这可能是由于在海相成岩作用的初始阶段中性至碱性作用以及减少了冲刷矿石中的水的作用。海底再沉积以及生物活性驱动的硫化物再加工的广泛证据表明，在动态构造环境中，从近端VMS过渡到了由再沉积过程形成的更远端的沉积类型。这种情况似乎与在开放初期将侏罗纪利古里亚海解释为狭窄的盆地相一致，其现代类似物在红海中。

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