Mineral Inclusions in Diamonds from the Sloan Kimberlites, Colorado
Mineral Inclusions in Diamonds from the Sloan Kimberlites, Colorado
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科罗拉多州斯隆金伯利岩钻石中的矿物包裹体
DOI：
10.1086/629062
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
M. Mccallum
中科院分区：
文献类型：
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作者：
H. Meyer;M. Mccallum
在科罗拉多北部的斯隆1号和2号金伯利岩管道中，从40颗小（<1.5毫米）钻石中发现了矿物包裹体。原生包裹体（即原或同生包裹体）为橄榄石、斜辉石、银石、金红石，可能还有原生铁和一些绿云母。被解释为后成因的相有钛铁矿、辉长石、大部分绿云母、钙钛矿、锰钛矿、铬尖晶石、磁铁矿、方解石、蛇纹石，可能还有镁钛矿。钛矿、黄铁矿和钙钛矿在金刚石中未见报道。后成矿物通常以包裹体组合形式出现，如：绢云母+辉黄铁矿、绢云母+钙钛矿+钛铁矿+磁铁矿+蛇纹石、绢云母+斜辉石+尖晶石+磁铁矿+方解石等。大多数原生包裹体具有辉绿岩套件亲和性，这种情况并不常见，但与非洲南部和中部的Premier、Orapa和Mbuji Mayi金伯利岩以及俄罗斯和西澳大利亚的一些地点的钻石相似。次生包裹体反映了金伯利岩流体的广泛蚀变和结晶作用，以及至少一些侵入后地下水引起的蚀变。表观成因组合包裹体的丰度与科罗拉多钻石的大量破裂、断裂和破碎性质有关。一些后成包裹体可能是上地幔交代事件的产物，在这个交代事件中，marid型矿物可能沿着原生包裹体产生的裂缝被引入钻石中。大多数裂缝和断裂可能是在浅的、早期的或先发制人的事件中形成的。
Mineral inclusions have been recovered from 40 small (<1.5 mm) diamonds from the Sloan 1 and 2 kimberlite pipes in northern Colorado. Primary inclusions (i.e., proto- or syngenetic) are olivine, clinopy-roxene, sanidine, rutile, and possibly native Fe and some phlogopite. Phases interpreted as epigenetic are acmite, richterite, most phlogopite, perovskite, Mn-ilmenite, Cr-spinel, magnetite, calcite, serpentine and possibly Mg-ilmenite. Acmite, richterite, and perovskite have not previously been reported in diamond. The epigenetic minerals commonly occur as inclusion assemblages such as phlogopite + richterite, phlogopite + perovskite + ilmenite + magnetite + serpentine, and phlogopite + clinopyroxene + spinel + magnetite + calcite. The majority of the primary inclusions have an eclogitic suite affinity, which is uncommon but similar to diamonds in the Premier, Orapa, and Mbuji Mayi kimberlites of southern and central Africa and from a few sites in Russia and Western Australia. Secondary inclusions reflect extensive alteration by, and crystallization of, kimberlite fluids and at least some post-intrusive ground water induced alteration. The abundance of epigenetic assemblage inclusions is related to the cracked, fractured and broken nature of large numbers of the Colorado diamonds. Some epigenetic inclusions may be products of a metasomatic event in the upper mantle in which MARID-type minerals may have been introduced into diamonds along cracks generated by primary inclusions. Most cracks and fractures probably formed during a shallow, early or pre-emptive event.