The Evaluation On The Metallogeneisis Of The Ultrabasic Rocks In The Eastern Part Of Dingqing Suture Zone,Tibet

Dingqing suture is in the eastern part of the Bangonghu-Nujiang terrane zone where the Bangonghu-Nujiang Ophiolite mélange zone, the plate juncture of India plate and the Eurasian plate, is located. The ultramafic-mafic rocks in this area exhibit a wider zonal distribution along the direction of NW-SE. This Ultrabasic rock belt lies between the Bangonghu-Nujiang deep faults and Lancang River deep faults. The geological condition of mineralization in this spot is superior and the development of Cu?Ni?Cr and PGE(Platinum Group Elements) anomaly is obvious. In recent years, with the discovery of nickel sulfide ore in the Bannu west, several other copper nickel ore deposits later successively found in the east, these sites are all distributed in the rock belt zone where a great potential for mineral exploration is expected.This paper chooses to study the rock body of Ninilaka?Lasangka?Xieqionglong? Leyinka and Xiegala to carry out systematic research on the evaluation of metallogenic properties, Petrology and Geochemistry. Each rock body from this area is well analyzed and summarized and a preliminary evaluation is given for their potential of mineralization.The petrologic and geochemical research have shown that the alteration of the rock body of Ninilaka?Lasangka and Xieqionglong is intense in overall, developed serpentinization, occasional carbonatization; exhibiting the characteristics of rich in magnesium?poor in alkali?poor in aluminum, and specially poor in calcium and titanium; rock m/f ratio >9.0, belongs to Magnesian ultra-basic rock; rock Mg# value >0.90, belongs to residue mantle magma; REE(Rare Earth Element) shows depleted mantle, which has Eu negative anomaly in general, REE distribution points curve displays a right-oblique type in wide and flat shape; alteration of Leyinka and Xiegala rock body is intense, developed sodium zoisitization and sericitization; exhibiting the characteristics of rich in magnesium, relatively poor in alkali, and poor in aluminum and calcium; it belongs to rich iron ultra-basic rock; Mg# average value of the rock is 0.58, it is the product of primary magma via the process of magmatic crystal fractionation; REE distribution model obviously shows the right-oblique type, the content of REE in overall is lower, Eu anomaly basically is not displayed.The rock body of Ninilaka, Xieqionglong and lasangka has similar REE distribution patterns that displays strong characteristics of depleted mantle; the rock body of leyinka and Xiegala also has similar REE distribution curve pattern, when compared with typical MORB, the geochemical characteristics of REE is similar, reflecting the fact that they came from the depleted asthenospheric mantle; the obvious enrichment of TH indicates that the magma was contaminated by crustal materials during the process of ascending and intrusion.Through the study of favorable lithofacies zoning?geochemical features of the rock(rock m/f ratio?field mineralization clues?traces of microelement and the degree of magmatic differentiation and crystallization) metallogenesis index, a preliminary evaluation has been carried out for the metallogenic properties of the rock body of Lasangka?Xieqionglong?Ninilaka?Leyinka and Xiegala within the region of study. Through the comprehensive analysis, The harzburgite lithofacies in the study area is a favorable rock facies for the mineralization of chrome iron ore, this lithofacies zone contains rock bodies of Ninilaka and Lasangka, which is a better geological condition for mineralization; the mineralization potential for the Olivine pyroxenolite lithofacies belt(the rock body of Xieqionglong) is generally poor; from the lithofacies zoning and the analysis on the geochemical features of the rock, gabbro lithofacies zone(the rock body of Leyinka) and the diabase dyke(dike) lithofacies zone(the rock body of Xiegala) have a relatively smaller mineralization potential.