Origin and Significance of Ilmenite Megacrysts and Macrocrysts from Kimberlite
Origin and Significance of Ilmenite Megacrysts and Macrocrysts from Kimberlite
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钛铁矿巨晶和金伯利岩粗晶的起源和意义
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
C. Hetman
中科院分区：
文献类型：
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作者：
D. Schulze;P. N. Anderson;B. C. Hearn;C. Hetman
对北美26个金伯利岩中的钛铁矿(巨晶和巨晶)进行了电子探针分析，以帮助了解世界各地金伯利岩中钛铁矿的成因和意义。大多数属于贫铬的巨晶套间。贫铬系列钛铁矿的地球化学趋势与地幔分离结晶成因相一致，钛铁矿只占结晶组合的一小部分。共沉淀镁矿是镁的重要宿主，其结晶导致共存的钛铁矿中镁的贫化。金伯利岩上升过程中菱镁矿巨晶的剥蚀作用可能使金伯利岩富含镁，从而导致钛铁矿边缘镁含量的增加。钛铁矿边缘的赤铁矿含量通常低于岩心，这表明如果仅考虑岩心成分，金伯利岩的氧化状态可能被高估，从而可能高估其钻石再吸收的潜力。不..。
Ilmenite populations (megacrysts and macrocrysts) from 26 kimberlites in North America have been characterized by electron microprobe analysis to assist in the understanding of the origin and significance of ilmenite in kimberlites worldwide. Most belong to the Cr-poor megacryst suite. Geochemical trends in Cr-poor-suite ilmenites are consistent with a mantle fractional crystallization origin, with ilmenite forming only a minor proportion of the crystallizing assemblage. Coprecipitating magnesite is inferred to be an important host for Mg, with its crystallization causing Mg depletion in coexisting ilmenite. Decrepitation of magnesite megacrysts during kimberlite ascent may have enriched kimberlite hosts in Mg, contributing to the Mg increase characteristic of ilmenite rims. Ilmenite rims commonly have lower hematite contents than do cores, suggesting that the oxidation state of the kimberlite, and thus its potential for diamond resorption, can be overestimated if core compositions alone are considered. N...