Graphite-sulfide deposits in Ronda and Beni Bousera peridotites (Spain and Morocco) and the origin of carbon in mantle-derived rocks
Graphite-sulfide deposits in Ronda and Beni Bousera peridotites (Spain and Morocco) and the origin of carbon in mantle-derived rocks
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DOI：
10.1016/j.gr.2005.10.003
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发表时间：
2006-04-01
影响因子：
6.1
通讯作者：
Gervilla, F.
中科院分区：
文献类型：
--
作者：
Crespo, E.;Luque, F. J.;Gervilla, F.
本文描述了在西班牙Serrania de Ronda和摩洛哥贝尼Bousera超镁铁质岩中发现的不寻常的石墨硫化物矿床。这些矿床以矿脉、网脉和不规则团块的形式出现，厚度从几厘米到几米不等。原生矿物组合主要由Fe-Ni-Cu硫化物（磁黄铁矿、镍黄铁矿、黄铜矿和立方铜矿）、石墨和铬铁矿组成。风化发生在一些由石墨（高达90%）、铬铁矿和针铁矿组成的贫硫化物矿床中。在结构上，石墨可以作为薄片或薄片簇以及作为圆形的结节状聚集体出现。石墨是高度结晶的，并且显示出轻的碳同位素特征（Δ C-13近似高达千分之-15至千分之-21）。有时，一些结节状石墨聚集体显示出较大的同位素分区，具有较重的立方形式（可能是金刚石之后的石墨假晶，δ C-13高达-3.3ppm），向外被逐渐变轻的薄片（δ C-13高达-15.2ppm）覆盖。软流圈熔体起源于橄榄岩和辉石岩的部分熔融（和熔体-岩石反应），产生残余熔体，形成石墨硫化物矿床。这些残余熔体集中挥发性组分（主要是CO2和H2O），以及S，As和亲铜元素。含石墨（以前的金刚石）的加纳辉石岩与渗透的软流圈熔体的熔体-岩石反应将碳结合到熔体中。富石墨石榴辉石岩是由俯冲的富含干酪根的地壳物质向地幔的超高压转化而形成的。因此，在大多数研究的矿点中，石墨具有轻（生物）碳特征。在当地，反应的轻碳在熔体中的残余物的C-130富集石墨化的金刚石（可能产生的热液方解石脉在俯冲洋壳）与部分熔体反应，形成同位素分区结核状石墨聚集体。(c)2005年国际冈瓦纳研究协会。Elsevier B. V.出版，保留所有权利。
This paper describes unusual graphite-sulfide deposits in ultramafic rocks from the Serrania de Ronda (Spain) and Beni Bousera (Morocco). These deposits occur as veins, stockworks and irregular masses, ranging in size from some centimeters to a few meters in thickness. The primary mineral assemblage mainly consists of Fe-Ni-Cu sulfides (pyrrhotite, pentlandite, chalcopyrite and cubanite), graphite and chromite. Weathering occurs in some sulfide-poor deposits that consist of graphite (up to 90%), chromite and goethite. Texturally, graphite may occur as flakes or clusters of flakes and as rounded, nodule-like aggregates. Graphite is highly crystalline and shows light carbon isotopic signatures (delta C-13 approximate to up to -15 parts per thousand to -21 parts per thousand). Occasionally, some nodule-like graphite aggregates display large isotopic zoning with heavier cubic forms (probably graphite pseudomorphs after diamond with delta C-13 Up to -3.3 parts per thousand) coated by progressively lighter flakes outwards (delta C-13 up to -15.2 parts per thousand). Asthenospheric-derived melts originated the partial melting (and melt-rock reactions) of peridotites and pyroxenites generating residual melts from which the graphite-sulfide deposits were formed. These residual melts concentrated volatile components (mainly CO2 and H2O), as well as S, As, and chalcophile elements. Carbon was incorporated into the melts from the melt-rock reactions of graphite-bearing (formerly diamonds) garner pyroxenites with infiltrated asthenospheric melts. Graphite-rich garnet pyroxenites formed through the UHP transformation of subducted kerogen-rich crustal material into the mantle. Thus, graphite in most of the studied occurrences has light (biogenic) carbon signatures. Locally, reaction of the light carbon in the melts with relicts of C-130-enriched graphitized diamonds (probably generated from hydrothermal calcite veins in the subducting oceanic crust) reacted with the partial melts to form isotopically zoned nodule-like graphite aggregates. (c) 2005 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.