In the Kenticha area,a series of barren to rare metal-bearing pegmatites intruded into the Neoproterozoic Adola Belt.The pegmatites host world-class Nb and Ta deposits and significant Li and Be reserves.In this contri-bution,fluid inclusion data and feldspar geothermometry have been combined to define the crystallization condition of the Kenticha rare-metal pegmatite.Primary and com-plex assemblages of secondary fluid inclusions represent-ing episodic fluid circulations have been identified in quartz and spodumene.A primary aqueous-carbonic fluid of low salinity aqueous solution with liquid and vapour CO2 phases,secondary carbonic fluid rich and carbonic-only fluids,and multiple generations of secondary aqueous inclusions that represent sub-solidus hydrothermal circu-lation have been identified.All aqueous inclusions were homogenized into the liquid phase between 100 and 290℃.Aqueous-carbonic inclusions were homogenized,usually via a critical transition[Th(LV → SCF)]between 241 and 397℃,or less commonly,via a dew-point tran-sition[Th(LV → V)]between 213 and 264℃.Crystal-lization of the rare-element pegmatite is certainly associated with the late-stage magmatic or early hydrothermal low-salinity aqueous-carbonic fluid that homogenizes to critical conditions.A combination of microthermometric data and existing experimentally determined solidus from flux and volatile bearing haplo-granite suggests exsolution of fluids from hydrous silicate melt,perhaps during crystallization of the aplitic layer.The fluids were then trapped and isobarically cooled along a reasonable geothermal gradient within the pegmatite unit down to a temperature of around 397℃.

Barsisa Bekele;Amit Kumar Sen

Department of Earth Sciences,Indian Institute of Technology Roorkee,Roorkee,India;Department of Earth Sciences,Wollega University,Nekemte,Ethiopia

地球化学学报（英文版）

[1]Barsisa Bekele;Amit Kumar Sen-.Fluid inclusion studies of the Kenticha rare-element granite-pegmatite,Southern Ethiopia)[J].地球化学学报（英文版）,2022(06):926-946

Kenticha,pegmatites,Adola,geothermometry,homogenizes,microthermometric,aplitic,isobarically

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