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UHP-05 General topics of geology, tectonics and petrology of collisional orogenic belts: Implication to UHP-HP metamorphic rocks
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Preliminary research on Kangjinla podiform chromite deposit in Tibet
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Xiang zhen Xu, Key Laboratory for Continental Dynamics, Institute of Geology, CAGS (China)
Jingsui Yang, Key Laboratory for Continental Dynamics, Institute of Geology, CAGS (China)
dengzhu Ba, Key Laboratory for Continental Dynamics, Institute of Geology, CAGS (China)
Qingsong Fang, Key Laboratory for Continental Dynamics, Institute of Geology, CAGS (China)
Songyong Chen, Key Laboratory for Continental Dynamics, Institute of Geology, CAGS (China)
Wenji Bai, Key Laboratory for Continental Dynamics, Institute of Geology, CAGS (China)
Huaqi Li, Key Laboratory for Continental Dynamics, Institute of Geology, CAGS (China)
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The Luobusa chromite deposit occurs in the Luobusa ophiolite in the east segment of the Yarlungzangbu ophiolite belt. The ultramafic blocks are strictly controlled by faults and as tectonic blocks in the Tertiary Luobusa Group. The deposit is located, between Sangri County and Jiacha County of Shannan City. The Luobusa ophiolite is mainly composed of mantle peridotite, cumulate, basic dyke and basaltic lava. The mantle peridotites, which are the host rock of podiform chromite deposits, are mainly composed of harzburgite, dunite and lherzolite. The compositional features show that the Luobusa mantle peridotites belong to highly depleted mantle with a constant low abundance of REE and an upside down "V" shape of chondrite normalized REE pattern. The cumulates are mainly consisted of wehrlite, lherzolite, clinopyroxenite and gabbro. The chromite deposits in the Luobusa ophiolite can be divided into three deposits from west to east. They are named the Luobusa deposit, the Xiangkashan deposit and the Kangjinla deposit. Less geological research has been performed on the Kangjinla deposit than the Luobusa and the Xiangkashan deposits due to high elevation and poor road condition. This paper is going to report some preliminary results from the Kangjinla deposit.
Similar to the Luobusa deposit, the chromite ore bodies in Kangjinla always have a thin dunite shell, and the lithologic boundary between chromite deposit and dunite is clear without faulting. There are different types of ores in Kangjinla, including nodular, disseminated and massive types, in which nodular ores are dominated. Nodular ores are usually associated with massive ores and, in some cases they can be elongated and oriented. The nodular ores are rounded or elliptical with a common diameter of 1∼3 cm. A 1500 kg chromite sample and a 500 kg peridotite sample were collected from No. 13 orebody in Kangjinla. After careful washing and mineral separation, a series of heavy minerals were picked out through a binocular microscope, including silicates, oxides, sulfides, metal alloys, native elements and carbonates. It is notable that a large amount of diamond were first discovered from the Kangjinla chromite deposit, as well as many other unusual minerals, such as moissanites, rutiles, native irons and metal alloys.
In general, the mineral assemblages in the Kangjinla chromite deposit are comparable to those in the Luobusa chromite deposit. But the work has just been started, and lots of detail measurements are required in further work.
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