The metallogenic mechanism of rare metal deposits in the Dahongliutan ore field,Hotian,Xinjiang
The Dahongliutan rare metal ore field,situated in the West Kunlun orogenic belt,is a significant component of the pegmatite belt of Songpan-Ganzi-West Kunlun.Seven large and medium-sized lithium-beryllium deposits,including the Bailongshan,509 Daobanxi,Dahongliutan East and 507 lithium deposits,have been discovered in this area,with a total Li2O reserve of over 1 million tons and even a greater mineralization potential.This article provides a comprehensive summary of the mineralization characteristics and processes within the Dahongliutan pegmatite field.Our findings reveal that:(1)The granitic pegmatite and the Dahongliutan pluton were formed in the Late Triassic,with a close spatial relationship.Additionally,there is a zoning pattern observed,with microcline pegmatites(mineral composition of microcline,quartz and muscovite)transitioning to spodumene pegmatites(mineral composition of spodumene,albite,quartz and muscovite)from the Dahongliutan pluton to its distal end.Most of the spodumene pegmatites are concentrated within 1～2km of the outer contact zone of the Dahongliutan pluton.(2)Differences of geochemical compositions,and εHf(t),εNd(t)and δ7 Li values among quartz diorite,biotite adamellite and two-mica adamellite indicate they have distinct sources,albeit they have the same syn-collision tectonic background during the Late Triassic.(3)The consistency in ages and Hf and Li isotopic characteristics between pegmatite and two-mica adamellite suggests a shared origin from a muscovite-rich metasediment source through muscovite dehydration melting.(4)The initial pegmatite-forming melts are rich in fluxing elements,such as P,B,F and alkali metal elements,which enhance the solubility of H2 O in the melt,facilitating the enrichment of Na,Li and alkali metal elements,thus forming a lithium-rich pegmatite-forming melt.(5)Space relations,geochemistry and Li isotope characteristics indicate that fractional crystallization may not occur between granite and granite pegmatite,but they may form due to the immiscibility of the same granitic magma.In summary,melt-fluid separation during the transport of volatile-and alkali metal-rich pegmatite-forming melt may result in the extraordinary enrichment of rare metal elements.The periphery of the Dahongliutan pluton,particularly within 1～2 km of the outer contact zone of the two-mica adamellite,presents a favorable area for exploring the spodumene pegmatites.
万方数据
维普
