Assessment Of Diamond Mineralization Geological Condition In Southwest Of Hetian Area, Xinjiang

This paper is part of the National Geological Survey Project "The evolution of the western Kunlun and minerals", which is held by Zhao Lei. The degree on geological research is very low in northwest Hetian Area of Tarim Platform. According to the relevant records, 8 diamonds had been found from 1945 to 1966 in Hetian area of Xinjiang;but only one disputable pyrope had been found through repeatedly diamond prospecting. In this paper, basing on the exhaustive study of the natural heavy minerals, taking the conditions of geotectonic evolution and aeromagnetic survey into account, the author tries to assess the diamond geological conditions and points out the way of diamond prospecting.Through electron microprobe analytical technique, garnets, chromites, pyroxenes, ilmenites and olivines are qualitatively and quantitatively studied in this paper. According to the index mineral assemblage, this area lacks of pyrope and geikielitem, while chromspinellide is very rich: which is the distinctive feature of lamproite. In addition, the eclogitic xenolith predominates the mantle xenoliths, and the peridotitic xenolith is secondary. So the native rock of diamond in this area may be lamproite.The mantle thermal state of studied area is calculated through geothermometers and geobarometers. The mantle temperature is high, but the pressure is too low to form diamonds.The aeromagnetic anomaly and the geotectonic evolution are also taken into account. Diamonds are found in Tertiary stream deposit terraces, so the original diamond ores should be formed before Tertiary period when north area was higher than south area and the rivers ran from north to south. It was in late-Tertiary or after this period that Tiekelike block was uplift and the rivers flow direction was reversed. So, primary diamond deposit should be in the north of the locations where diamonds have been found.Finally, this paper makes an assessment on mineralization geological conditions of diamonds and points out the way of diamond prospecting.