Fluorite Mineralization Related to Carbonatitic Magmatism in the Western Transbaikalia: Insights from Fluid Inclusions and Trace Element Composition

Anna A Redina,Ilya V Veksler,Cora C Wohlgemuth-Ueberwasser,Anna G Doroshkevich

doi:10.3390/min11111183

Abstract

Fluorite mineralization associated with different types of magmatism is common in the Western Transbaikalia. This study deals with Arshan, Yuzhnoe, and Ulan-Ude fluorite occurrences, which are the most significant examples of carbonatite-related fluorite mineralization in the region. The present paper focused on new fluorite geochemistry and fluid inclusion data, is aimed at revealing conditions of the fluorite mineralization formation, highlighting its genetic relationship with magmatism, compared to other deposits of this type. All the three locations belong to the Late Mesozoic Central Asian carbonatite province. Fluorites here are characterized by high rare earth elements (REE), Sr, and elevated La/Yb values. Fluid inclusions data imply that the formation of fluorite mineralization is a long process extending from late magmatic to the hydrothermal stage. Early fluorite crystallized from sulfate-carbonate orthomagmatic fluids at temperatures up to 500 °C. True hydrothermal fluorite was formed from the same fluids that were probably mixed with meteoric waters, which caused the temperature to drop to below 420 °C and led to an increase in the chloride component. The REE compositions of fluorite from the studied locations are similar to compositions of REE-rich fluorites from carbonatite-related deposits around the world.

Highlights

Carbonatite melts generally have anomalously high contents of F, rare earth elements (REE), Sr, P, U and other incompatible lithophile elements
We present first data on REE concentrations in fluorites, which help to establish a genetic link between fluorite mineralization and carbonatite magmatism, and conditions for the formation of fluorite mineralization
These fluorites have relatively flat chondrite-normalized REE spectra (Figure 2). They are characterized by depletion of light rare earth elements (LREE), as well as the absence of any obvious element anomalies

Summary

Introduction

Carbonatite melts generally have anomalously high contents of F, rare earth elements (REE), Sr, P, U and other incompatible lithophile elements. One of the most common minerals in carbonatite-related REE deposits worldwide is fluorite. Fluorite mineralization has been reported to form both at the magmatic (Mato Preto) [1] and the hydrothermal stages (Amba Dongar, Songwe Hill) [2,3]. Magmatic and hydrothermal fluorite occurs within the same deposit (e.g., Bayan Obo, Mushgai-Khudag) [4,5,6,7]. That is why trace element composition of fluorite and information obtained from studies of fluid inclusions in this mineral provide valuable insights for sources of fluid (e.g., magmatic versus formation waters), fluid composition, the deposition conditions, and make inferences about the ore potential of individual deposits

Results

Discussion

Conclusion