Geological features and ore-forming mechanism of the Qiongjiagang super-large pegmatite lithium deposit in Himalaya,China
The Tibetan Himalayan Qiongjiagang pegmatite-type lithium deposit is a landmark rare-metal deposit in the Himalayan belt.Uncovering the geological characteristics of the mineralization,the mechanism of mineralization,and the evaluation of mineral directors in the pegmatites will be of great significance to the research on the formation mechanism and prospecting of the Himalayan rare metal belt.Institute of Geology and Geophysics,Chinese Academy of Sciences(IGGCAS)has made the following findings on the formation mechanism of the Himalayan Qiongjiagang pegmatite-type lithium deposit in 2021～2023:(1)the main ore body of the Qiongjiagang spodumene pegmatites mainly occurred along the foliation of the skarnization marble and calcareous phyllite strata,and the central part of the main ore body is generally sub-horizontal,with large dips on both sides of the main ore body;(2)the ore minerals in the Qiongjiagang ore bodies consist of spodumene(including three stages),petalite,cookeite,lepidolite,beryl,helvite,bertrandite,columbite-group minerals and cassiterite;(3)the evolution and mineralization characteristics of the Qiongjiagang granite-pegmatites are controlled by the fractional crystallization and differentiation processes,the fluid exsolution is genetically related to the lithium mineralization,and the magma source may be saturated with rare-metal elements at the early stage of granitic melt evolution;(4)K-feldspar Ti thermometer and isochores from microthermometric measurement of the fluid inclusions show a temperature decreasing trend from tourmaline leucogranite granite to spodumene pegmatite,and depressurization in the formation of the spodumene pegmatites by estimating pressure-temperature conditions(trapping temperature:ca.410～475℃;trapping pressure:ca.180～240MPa);(5)establish the ore deposit model of Qiongjiagang lithium deposit,pointing out that the high degree of crystallizing differentiation,fluid exsolution and depressurization drive the formation of the Qiongjiagang spodumene pegmatites,and late-magmatic metasomatism is responsible for the formation of rare-metal mineralization;(6)Feldspar composition(Rb,Cs,Sr,Ba,K/Rb and formation temperature),garnet composition(high-water content and high Mn/(Mn+Fe)ratio),and paragenesis and types of mineral inclusions in the accessary minerals are effective indicators for evaluating of the mineralization of the Qiongjiagang pegmatites.
Qiongjiagang lithium depositGeological featuresOre-forming mechanismOre deposit modelHimalayan rare-metal metallogenic belt
万方数据
维普
