Two diamond-bearing peridotite xenoliths from the finsch kimberlite, South Africa
Two diamond-bearing peridotite xenoliths from the finsch kimberlite, South Africa
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产自南非芬什金伯利岩的两块含钻石橄榄岩捕虏体
DOI：
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发表时间：
1982
期刊：
影响因子：
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通讯作者：
D. Robinson
中科院分区：
文献类型：
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作者：
S. Shee;J. Gurney;D. Robinson
在Finsch矿发现的两个含金刚石捕虏体是粗石榴石橄榄岩，其结构和化学性质与该金伯利岩中主要的地幔捕虏体相似。其中一颗钻石共出土46颗，重0.053克拉，另一颗钻石共出土53颗，重0.332克拉。这些钻石比从金伯利岩中开采出来的钻石腐蚀得更少。地温压计算表明，捕虏体在~ 1130°C和50 kb压力下达到平衡，在金刚石稳定场范围内；这相当于160公里的深度，并且将岩石放置在一个盾状地热上，其深度略高于金伯利岩中大多数粗石榴石橄榄岩。这两种岩石中的原生矿物彼此非常相似，但与芬兰钻石中的大多数矿物包裹体明显不同。这表明金伯利岩中的钻石和包体中的钻石有不同的起源，尽管这两套的平衡条件大致一致，接近于“湿”橄榄岩固相。
Two diamond bearing xenoliths found at Finsch Mine are coarse garnet lherzolites, texturally and chemically similar to the dominant mantle xenoliths in that kimberlite. A total of 46 diamonds weighing 0.053 carats have been recovered from one and 53 diamonds weighing 0.332 carats from the other. The diamonds are less corroded than diamonds recovered from the kimberlite. Geothermobarometric calculations indicate that the xenoliths equilibrated at ∼1,130° C and pressures 50 kb which is within the diamond stability field; this corresponds to depths of 160 km and would place the rocks on a shield geotherm at slightly greater depths than most coarse garnet lherzolites from kimberlite. The primary minerals in the two rocks are very similar to each other but distinctly different to the majority of mineral inclusions in Finsch diamonds. This suggests a different origin for the diamonds in the kimberlite and the diamonds in the xenoliths although the equilibration conditions for both suites are approximately coincident and close to the “wet” peridotite solidus.