REE Geochemical Characteristics of Two Granite‐Derived Weathering Profiles, Guangxi, South China: Implications for the Formation of the Ion Adsorption Type REE Deposit

well documented because of its economical significance of hosting the ion adsorption type REE Deposit in South China (Wu et al., 1988; Bao et al., 2008; Yuan et al., 2012; Wang et al., 2013). Besides Jiangxi and Guangdong provinces, Guangxi province is regarded as another potential region for exploration and prospecting of the ion adsorption type REE Deposit, where there are at least 67 places of granite-derived weathering crusts have been found bearing the REE mineralization (Gao et al., 2009; Deng et al., 2011). However, the geological and geochemical characteristics of the REE-rich laterite crusts over the granite rocks in Guangxi province have not been fully studied. The present study deals with two newly discovered granite-derived weathering profiles located in Xiaoping Mountain, Yulin, Guangxi. We present a preliminary evaluation of our new data about REE geochemistry, which provide a detailed information about the REE-rich laterite crusts in Guangxi. Also, our work is useful for the future exploration of REE resources in this region. There are two types of granite rocks outcropping in the study area, comprising the fine-grained biotite adamellite (A type) and the coarse-grained biotite adamellite (B type). Both of them show similar weathering feathers. From the bedrock upward, three lithostratigraphic layers can be divided based on the variations in color, texture and mineralogy, and they can be termed as the surface soil layer, full-weathered layer and semi-weathered layer respectively. Geochemical analysis show that there are some marked differences in REE geochemistry between the laterite profiles derived from above mentioned two types bedrock. As for the laterite profile derived from the fine-grained biotite adamellite (A profile), there are various ΣREE contents along the profile showing as: 132ppm (mean value in the bedrock) →203ppm (mean value in the semiweathered layer) →180ppm (mean value in the fullweathered layer) →178ppm (mean value in the topsoil). There is a weak enrichment of REE in the full-weathered and semi-weathered layers with a enrichment factor between 1.4-1.5 comparative to the bedrock, and the highest value presents at 226ppm in the full-weathered layer. ΣLREE/ΣHREE throughout the weathering profile is ranging from 1.04 to 1.38. As for the laterite profile derived from the coarsegrained biotite adamellite (B profile), the variation of ΣREE is showing as: 342ppm (mean value in the bedrock) →569ppm (mean value in the semi-weathered layer) →474ppm (mean value in the full-weathered layer) →375ppm (mean value in the topsoil). REE is largely enriched in the full-weathered and semi-weathered layers, which is 1.4-1.7 times higher than that of the bedrock, and the highest REE value presents at 871ppm in the fullweathered layer. ΣLREE/ΣHREE in the weathering products are ranging from 1.10 to 5.74, indicating that LREE content is greatly higher than HREE in this weathering profile. Experimental analyses show that the vertical distribution of REE in both A and B profiles are closely related to soil pH and organic matter. The pH value shows a stable increasing trend from top to bottom with a range of 5.22-6.58 in A profile and a range of 4.90-6.58 in B profile respectively. The organic matter content show a decreasing trend from top to bottom, which is conversed comparing with the pH value, with a range of 4.89%0.63% in A profile and a range of 14.32%-0.62% in B FU Wei, YAN Xiaodong, LI Wei, ZHANG Yaqian, Zeng Xiangwei, 2014. REE Geochemical Characteristics of Two Granite-Derived Weathering Profiles, Guangxi, South China: Implications for the Formation of the Ion Adsorption Type REE Deposit. Acta Geologica Sinica (English Edition), 88(supp. 2): 433-434.