Mineralogical and Geochemical Characteristics of Triassic Lithium-Rich K-Bentonite Deposits in Xiejiacao Section, South China

Yongjie Lin,Jianming Xu,Enyuan Xing,Xinsheng Niu,Simon A T Redfern,Mianping Zheng,Yongsheng Zhang,Jiaai Zhong

doi:10.3390/min10010069

Yongjie Lin, Jianming Xu + Show 6 more

Open Access

https://doi.org/10.3390/min10010069

Copy DOI

Abstract

Widespread alteration in the Early–Middle Triassic volcanic ash of the Xiejiacao section, south China, has resulted in significant occurrences of lithium-rich K-bentonite deposits with economic potential. Detailed mineralogical and geochemical investigations of Li-rich K-bentonite deposits from the Xiejiacao section of Guangan city, South China, are presented here. The X-ray diffraction (XRD) data and major element chemistry indicates that the Li-rich K-bentonite deposits contain quartz, clay minerals, feldspar, calcite and dolomite, and the clay minerals are dominated by illite and ordered (R3) illite/smectite (I/S). The concentrations of major and trace elements in Li-rich K-bentonite deposits altered from volcanic ashes are most likely derived from felsic magmas, associated with intense volcanic arc activity. The composition of the clay components suggests that the Li-rich K-bentonite deposits are probably altered from the smectite during diagenesis, whereas smectite is mainly formed by submarine alterations of volcanic materials and subsequently the I/S derived from the volcanogenic smectite illitization. Moreover, accurate determination of the structure in I/S reveals that the temperatures reached by the sedimentary series are around 180 °C with a burial depth of ~6000 m. The widely distributed lithium-rich clay deposits strongly indicate widespread eruptions of volcanic ashes in the Early–Middle Triassic, which released huge amounts of volcanic ash. Lithium fixed in the illite and I/S is considered to have leached from the volcanogenic products by a mixed fluid source (i.e., meteoric, porewater and hydrothermal fluids). These Li-rich clay minerals in the marine basin contain economically extractable levels of metal and are a promising new target for lithium exploration.

Highlights

The increasing demand for lithium in rechargeable batteries, especially for electric vehicles, has attracted a great deal of interest in the search for more potential lithium resources
Several Li-rich clay beds have been found in the outcrop of Early–Middle Triassic strata in Sichuan Basin [7], only limited detailed studies have been published about the mineralogical and geochemical characteristics of mung bean rock
The illite is non-expandable and characterized by an intense broad d001 peak at around 10 Å, with further peaks at 5 Å and 3.33 Å in the low-angle region, which remain unchanged in all three X-ray diffraction (XRD) patterns

Summary

Introduction

The increasing demand for lithium in rechargeable batteries, especially for electric vehicles, has attracted a great deal of interest in the search for more potential lithium resources. Minerals 2020, 10, 69 and weathering origin, the global occurrence of lithium-rich clay deposits has rarely been reported, especially in large marine basins [2,3]. “Mung bean rock” (or “green bean rock”), a type of Li-rich clay deposit, is distributed widely in Early–Middle Triassic strata of south China, over an area of around. 700,000 km2 ,and dozens of centimeters to tens of meters in thickness [4] It is so called “mung bean rock” because of its green color and often contains siliceous clasts [5,6]. Several Li-rich clay beds have been found in the outcrop of Early–Middle Triassic strata in Sichuan Basin [7], only limited detailed studies have been published about the mineralogical and geochemical characteristics of mung bean rock. In particular little is known about their formation conditions and the supernormal enrichment mechanism of lithium [2,6,7,8]

Methods

Results

Conclusion