Geochronology, geochemistry of lamprophyre and evidence of mantle fluid in the western part of Xiangshan uranium orefield

This paper is the result of mineral exploration engineering.

Objective Mantle−derived magma generally provied an object to reveal geodynamic evolution in the depth and uranium mineralization. The mafic dikes in the west of Xiangshan uranium deposit are regarded as a key aspect to understand the regional tectono−magmatic evolution and uranium mineralization.

Methods In this paper, the comprehensive research of petrology, geochronology and geochemistry were carried on the lamprophyre in the west of Xiangshan uranium deposit.

Results There are three stages of lamprophyre in this area, which are 134 Ma, 120–125 Ma and 84.5 Ma. The lamprophyre is sodium−alkaline lamprophyre and characterized with the enrichment of LILE and LREE, depletion of HFSE, and obvious negative anomaly of Ta–Nb–Ti. The lamprophyre is the product of partal melting from the source region and crystallisation differentiation, which experienced the crystallization differentiation of olivine and clinopyroxene as well as strong assimilation and contamination of upper crustal meterials during the magmatic intrusion. The lamprophyre was formed in the extentional entraplate tensioned tectonic environment, and was not affected by the subduction of the ancient Pacific Plate. The source region is a mixture of asthenospheric depleted mantle (main source) and lithospheric enriched mantle, which is mainly characterized by asthenospheric depleted mantle.

Conclusions The first period of lamprophyres is much older than the age of uranium mineralization, only providing favorable conditions for uranium accumulation. The later two periods of lamprophyres are closely associated with uranium deposits on space and time, possibly providing mantle hydrothemal fluids (∑CO₂ and He) and a favorable reducing environment for uranium enrichment and deposition.