Discovery of the Gangbu spodumene-bearing pegmatite in the Shisha Pangma region and its geological significance
In recent years,the research and prospecting of Himalayan rare metal mineralization have made significant breakthroughs,making Himalaya an important rare metal mineralization belt in China.This paper reports the first outcrop discovery of spodumene-bearing pegmatite in the Shisha Pangma region.The outcropped spodumene-bearing pegmatite locates in the Gangbu region on the northeast side of Gyirong pluton,separating Tsalung valley of Gyirong area by the mountain peaks.The Gangbu spodumene-bearing pegmatite is another lithium ore occurrence after the discovery of spodumene-bearing pegmatite at the Qunggya Kang(Pusila),Gabo,Ra Chu,and Ku Chu regions.Considering the magma in the Tsalung valley of Gyirong area experiencing an extremely high degree of fractionation,the northern part of the Gyirong pluton should have an excellent prospect for rare metal mineralization.The mineralized pegmatite intruded into the metamorphic strata(biotite schist and vesuvianite-bearing skarn)at an altitude of 5300m.The spodumene-bearing pegmatite can be classified into two types according to the field occurrence:one is the strongly deformed pegmatite,which is strongly mylonitized and becomes lenses within the strata;the other is the weakly deformed pegmatite,which is weakly deformed with a relatively larger scale,but its strike is broadly parallel to the bedding plane.Combined with the metamorphic and deformation characteristics of the strata,we propose that this is the location of the development of the South Tibetan Detachment System(STDS).Below the mineralized pegmatite,tourmaline-bearing granitic pegmatite that cross-cutting the bedding and beryl-bearing pegmatite are exposed at an altitude of 5200m,and tourmaline-muscovite granite is exposed at an altitude of 5100m.The dating results of monazite and columbite-group minerals show that the age of the tourmaline-muscovite granite and two-types of spodumene-bearing pegmatites are 25Ma,and the age of the tourmaline-bearing granitic pegmatite that cutting across the bedding is 17.5Ma.The Mn#[Mn/(Mn+Fe)]values of columbite-group minerals in the Gangbu spodumene-bearing pegmatites are significantly higher than the columbite-group minerals in the 17.5Ma granitic pegmatite,and are also higher than the columbite-group minerals in other known pegmatites in the Himalayas,indicating that the pegmatitic magma here is relatively fluorine-rich.The Gangbu spodumene-bearing pegmatite is coeval with the Qunggya Kang(Pusila)and Ku Chu spodumene-bearing pegmatite pegmatites,suggesting that～25Ma is a critical lithium mineralization period in the Himalayan belt,which is closely related to the activities of the STDS.Spatially,the characteristics of cross-section in the Gangbu are similar to those in the Qunggya Kang(Pusila)and the Gabo,with the bottom part of the cross-section being a tourmaline-bearing leucogranite,the middle part being beryl-bearing pegmatite,and the top of cross-section being spodumene-bearing pegmatite.The occurrence of spodumene-bearing pegmatite is obviously controlled by the STDS,which reflects that lithium mineralization is spatially coherent along the strike of the Himalayan belt.Such a fact is of great significance to understanding the formation and exploration of rare metals mineralization in the Himalayan belt.
HimalayaNyalamGyirongspodumene-bearing pegmatiterare-metal elements
NETL
NSTL
万方数据
维普
