Development of Framboidal Pyrite During Diagenesis, Low-Grade Regional Metamorphism, and Hydrothermal Alteration
Development of Framboidal Pyrite During Diagenesis, Low-Grade Regional Metamorphism, and Hydrothermal Alteration
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DOI：
10.2113/gsecongeo.104.8.1143
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发表时间：
2009-12
期刊：
影响因子：
5.8
通讯作者：
R. Scott;S. Meffre;J. Woodhead;Sarah E. Gilbert;R. Berry;P. Emsbo
中科院分区：
文献类型：
--
作者：
R. Scott;S. Meffre;J. Woodhead;Sarah E. Gilbert;R. Berry;P. Emsbo
内华达州卡林走向北部和维多利亚州中部福斯特维尔的古生代沉积母岩中的草莓状黄铁矿与金矿床的分布模式、微观结构关系和成分变化共同表明，它并非全部是同沉积早期成岩起源。草莓状黄铁矿也在数公里深度处形成的热液脉中成核，并沿着变质作用期间形成的溶蚀面（缝合线和圆齿解理）成核，直至变质级（即葡萄石斑岩相）。在这些不同环境中形成的草莓状体的尺寸范围或内部形态没有明显差异，这表明单一的、相对简单的结晶路径可能在上地壳的较宽深度范围内运行。在福斯特维尔，异常富含金属（包括金）的草莓状黄铁矿在层状剪切脉附近最为丰富，这些剪切脉是在沉积主岩折叠过程中沿层理表面滑动而形成的。草莓状黄铁矿和其他类似分布的早期形成的硫化物的微观结构关系和 Pb 同位素组成，支持了 440 至 400 Ma 区域变形期间富含金属的 H 2S 热液局部间歇性流入的响应。这些发现可能对其他类似变形的变沉积层序具有影响，其中含金的草莓状黄铁矿的发现最近被引用作为沉积过程中金显着富集的证据。 © 2009 经济地质学家协会，Inc.
Distribution patterns, microstructural relationships, and compositional variations for framboidal pyrite in the Paleozoic sedimentary host rocks to gold deposits on the northern Carlin trend, Nevada, and at Fosterville in central Victoria, collectively demonstrate that it is not all of synsedimentary-early diagenetic origin. Framboidal pyrite also nucleated in hydrothermal veins formed at several kilometers depth and along dissolution surfaces (stylolites and crenulation cleavages) formed during metamorphism at up to anchizonal grade (i.e., prehnitepumpellyite facies). There are no obvious differences in either the size range or internal morphology of framboids formed in these various settings, suggesting that a single, relatively simple crystallization path may operate over a wide depth range in the upper crust. At Fosterville, anomalously metal-rich (including Au) framboidal pyrite is most abundant adjacent to laminated shear veins that developed by slip along bedding surfaces during folding of the sedimentary host rocks. Microstructural relationships and Pb isotope compositions for the framboidal pyrite, and other similarly distributed, early-formed sulfides, support development in response to the localized, episodic influx of metal-enriched H 2S-bearing hydrothermal fluids during regional deformation between 440 and 400 Ma. These findings may have implications for other similarly deformed metasedimentary successions, where the discovery of Au-bearing framboidal pyrite has recently been cited as evidence for significant Au enrichment during sedimentation. © 2009 Society of Economic Geologists, Inc.