| Rare earth elements,as an important strategic mineral resources,have attracted world-wide attention?Nanling area is known as the"Rare Earth Kingdom",where the REE deposits are mainly granite weathering crust?Mineralization is mainly related to Caledonian,Indosinian and Yanshan granites?This study is based on a newly discovered weathering crust type REE deposit in the metamorphic rock terrene of Southern China?The deposit is developed in the Qingbaikou sedimentary tuff area,The tuff are thick,high in weathering and rich in rare earth content?It is a good parent rock type of weathering crust type REE deposit?The discovery of this deposit enriches the types of exogenic rare earth deposits and broadens the field of prospecting for the weathered crust type rare earth ore,which is of great significance for Jiangxi and even the whole country?But,At present,,there are few research data about the adsorption of rare earth minerals by metamorphic rocks,which need to be enriched?This study is supported by the national major project:three dimensional comprehensive exploration and deep metallogenic prognosis in the Chong Ling-Huichang mining area,Nanling?On the basis of the detailed field geological survey,a variety of modern analytical techniques have been applied to the systematic study of geology,petrology,mineralogy,geochemistry and zircon U-Pb dating?The geological characteristics of this new type of mineralization,the occurrence forms of rare earth elements,the characteristics of source rocks and diagenetic ages are determined.The main understanding is as follows:?1?The weathering crust is divided into humic layer,completly weathering layer,partly weathered layer and bedrock from top to bottom,and ore bodies mainly occur in the upper part of thecompleteweathering layer and the upper partly of semi weathered layer.?2?The main rare earth minerals and rare earth carrier minerals in this metamorphic rock area include monazite,yttrium ore,cerium ore,biotite,feldspar,apatite,and spearstone.Among them,K-feldspar contain REE 20.51-56.07ppm and plagioclase 4.92-61.19ppm.biotite 30.74-49.59ppm,Muscovite REE 20.47-26.79ppm.apatite REE>8000ppm,titanite REE>10000ppm,sphagite>apatite>feldspar>mica.?3?Zircon U-Pb dating shows that the metamorphic rocks in this area are formed during 830-875Ma.Belong to Qingbaikouan?Compared to the granite weathered crust type rare earth deposits studied in the past,the source rocks are mainly Caledonian,Indosinian and Yanshan granites,and the weathering mineralization age is infer from the third period to the Quaternary.?4?Overall characteristics of rock geochemistry,Metamorphic rocks in this area shows:Silicon rich?>60%?,high Al2O3>15%,Al2O3>Na2O+CaO+K2O,belongs to aluminum supersaturated series.High iron 5.9%,low Mg,Ca,high content of REE?REE 273×10-61218×10-6,The REE content in the metamorphic rocks is much higher than those in the weathered crust of the granite.?5?By means of microscopic statistical calculation and petrochemistry diagram,the original rocks of metamorphic rocks are recovered,and it is concluded that the original rocks of metamorphic rocks in this area are volcanic rocks.?6?There are three main forms of REE occurrence:independent REE minerals,isomorphism in mineral lattice,and ion adsorption phase in clay minerals. |
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