The Study On Skarn Features And Mineralization Of The Nameung Copper Polymetal Deposit, Vientiane Province,Laos

In this paper, on the basis of previous work and using the petrology, mineralogy and geochemistry methodologies, the geological characteristics of the ore deposit, mineralogy and geochemistry characteristics of the skarn rocks and analyzed the metallogenic material sources and the genesis of the ore deposit are studyed. The characteristics of trace elements and REEs in this deposit are compared with the trace elements and REEs of the rocks and ores from some of the typical skarn deposits along the middle to low Yangtze River regions in China, which has made clarified the main results as followings:Trace element characteristics of the skarn rocks indicate that, during the skarnization process an obvious Nb/Ta, Zr/Hf fractionation happened. Skarn in this area has characteristics of low maturity of the earth’s crust features. The extent of fractionation varies with sample’s skarnization, and showing varied degrees of skarnization of the samples.REE characteristics of the ore body indicate that, during the skarnization process a weaker Nb/Ta, Zr/Hf fractionation happened. Skarn has the characteristics of high maturity of the earth’s crust features. The skarn’s mineralization and alteration are relatively stronger and homogeneous. From the REE characteristics of the ore body, it is clear that the ore body has enriched LREE, and larger fractionated HREE, implying REE characteristics show the skarn has close relations with the hot fluids from the deep molten granitic magma. Comparisons of the REE characteristics among the granite, skarn, main ore body and the surrounding rock reveal that the ore materials have the same origin relations with the granite, and ore forming materials has originated from the deep granitic magma.Analysis of surrounding rock of the mining area show that, the main strata are crystalline limestone, which facilitate to forming skarn ore body, favorable space of the strata has provided good space for migration and sedimentation of ore-forming hot fluids. The ore-forming parent rocks in this area are the potassium feldspar granite and biotitic adamellite granite; the magmatic hydrothermal fluids contain Cu, Pb, Zn and other ore-forming metallic elements and provided the impetus for mineral activation and migration.Comprehensive analysis shows that, this ore deposit is a typical skarn type of metasomatic deposit. Granite has provided metallogenic material source and heat source as well. The contact zone of the granite with limestone played an important role in controlling ore body emplacement. Metallogenic material of ore deposits in this area mainly comes from deep magma.