Mineral inclusions in diamonds from the River Ranch kimberlite, Zimbabwe

Article Abstract:

Mineral inclusions in diamonds give important information about the crystallization of the continental mantle during its early history. Previous diamond inclusion (DI) studies on specimens from the Kaapvaal craton have focused on the cratonic mantle stabilized as early as 3.2 Ga, however kimberlites located in a younger area of the cratonic basement have come into production. Over 99% of mineral inclusions in diamonds from the River Ranch pipe in the Lat Archaen Limpopo Mobile Belt in Zimbabwe, are known to be phases of harzburgitic paragenesis. DI chemistry shows a small overlap with River Ranch kimberlite macrocrysts.

Diamonds, Inclusions

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Steady state geotherm, thermal disturbances, and tectonic development of the lower lithosphere underneath the Gibeon Kimberlite Province, Namibia

Article Abstract:

Thermobarometric investigation of upper mantle xenoliths of the Gibeon Kimberlite region reveal the prominent role of a kimberlite magma in carrying them to the Earth's surface. Majority of the coarse equant and mosaic-porphyroclastic xenoliths exhibit thermal equilibrium for the mantle, whereas the other coarse equant xenoliths portray an ongoing cooling state. A few porphyroclastic xenoliths show transient heating of the mantle, while the P-T values of some coarse equant xenoliths nears a geothermal gradient of 44 mW/sq m. Electron microprobe surveys enable analysis of tectonic elements.

Observations, Geology, Structural, Structural geology, Magma

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Nd, Sr, Pb, Ar, and O isotopic systematics of Sturgeon Lake kimberlite, Saskatchewan, Canada: constraints on emplacement age, alteration, and source composition

Article Abstract:

Rb-Sr dating of phlogopites isolated from Sturgeon Lake kimberlite, Saskatchewan, Canada points to a crytallization age of 98 Ma in accordance with the geological age. The Ar(super 40)/Ar(super 39) heating analysis of a phlogopite sample shows high amounts of excess argon indicating to an age of nearly 410 Ma. The results of oxygen and carbon isotopic analyses are discussed.

Natural history, Saskatchewan, Sturgeon, Missouri

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