Abstract

A new Massadou kimberlite field, was discovered in southeastern Guinea, near the town of Macenta. It consists of 16 poorly diamondiferous kimberlite dikes, ~1 m thick on average. The ore-controlling zone has a width of around 600 m, its orientation corresponds to the K-4 trend after S. Haggerty, and it is quite well detectable in satellite images. A thick laterite weathering profile has developed on the kimberlites. The main indicator minerals are pyrope, chromite, and ilmenite. Ilmenite grains have a zoned structure with a high-Fe core (hemoilmenite) overgrown by a parallel-columnar aggregate of Mg-ilmente rim resulting from interaction of the core phase with kimberlitic melt. The age of kimberlites is estimated as 140–145 Ma by analogy with those in adjacent areas. Dikes occur as an independent form of kimberlite magmatism in the Guinean–Liberian shield, rather than being roots of kimberlite pipes; therefore, the erosion cutout is relatively small and large-scale diamond placers should not be expected.

中文翻译：

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几内亚的新马萨杜金刚石金伯利岩田

摘要

在几内亚东南部靠近Macenta镇的地方发现了新的Massadou金伯利岩田。它由16个不良的钻石状金伯利岩堤构成，平均厚度约1 m。控矿区的宽度约为600 m，其方向与S. Haggerty之后的K-4趋势相对应，并且在卫星图像中可以很好地检测到。在金伯利岩上形成了厚厚的红土风化剖面。主要的指示矿物是pyrope，铬铁矿和钛铁矿。钛铁矿晶粒具有带芯铁与金伯利特熔体相互作用的平行柱状聚集的Mg-ilmente轮缘长满的高铁芯（偏锌铁矿）的分层结构。与邻近地区类似，金伯利岩的年龄估计为140-145 Ma。堤防是几内亚-利比里亚盾构中一种独立的金伯利岩浆作用形式，而不是金伯利岩管的根部。因此，侵蚀切口相对较小，不应期望使用大型金刚石砂矿。