Petrogeochemical Characteristics and Metallogenetic Potential of Epimetamorphic Rocks in South Jiangxi Province

Abstract

Epimetamorphic rocks and related weathered crusts are widely distributed in South Jiangxi province. Identifying the petrological and geochemical characteristics of epimetamorphic rocks has a significant effect on the metallogenetic potential analysis on ion-adsorption REEs deposits. At present, there is little research about the metamorphic rock ion-adsorbed rare earth deposits. Epimetamorphic rocks of Neoproterozoic to Cambrian age are widely distributed in this region. Petrological and geochemical methods are used to classify these epimetamorphic rocks. Results show that the epimetamorphic rocks in this region have a large age span, ranging from Qingbaikou to Devonian. Minor epimetamorphic rocks also occur in Jurassic strata. Neoproterozoic epimetamorphic rocks are most widespread and mainly include blastopsammite, metamorphic tuff, slate, phyllite, and schist. Blastopsammite and metamorphic tuff have the highest REEs content with average contents of 302 μg/g and 246 μg/g, respectively, and show the LREE enrichment patterns with LREEs/HREEs of 2.68-5.43. Monazite and xenotime are the two most common rare earth minerals found in the epimetamorphic rocks so far. The metamorphic tuffs in the area have a large outcrop thickness, high REE content and well-weathered crusts, which are good metallogenic parent rocks for ion-adsorbed rare earth deposits. Phyllite, schist and granulite have lower REE contents (>224 μg/g, on average), but they are resistant to weathering and thus have a low potential in forming REE ore bodies. This study was a preliminary discussion of ion-adsorption rare earth deposits related to epimetamorphic parent rocks, which provides basic information and reference for further studies and prospecting.

Keywords

• epimetamorphic rock
• rare earth elements
• weathered crust
• ion-adsorption ree deposit
• x-ray fluorescence spectrometry
• inductively coupled plasma-mass spectrometry