青海省东昆仑斑岩带新发现

Discovery of new porphyry belts in Eastern Kunlun Mountains,Qinghai-Tibet Plateau

东昆仑地块近年来陆续发现和勘探一些斑岩型矿床,显示斑岩成矿作用的重要性和斑岩型矿床的找矿潜力。笔者在东昆仑新近发现多条斑岩带,它们相互平行,呈NE向产出,规模不等,既可产于两条近EW向主干断裂带之间,又可穿越主干断裂带;既可产于昆南区、昆中区或昆北区,又可跨区产出;主要出露于昆中带和昆北带,又以东昆仑东段都兰地区和西段祁漫塔格地区为主。斑岩体于印支期集中产出,其中印支晚期成矿能力较强。花岗斑岩主要为高钾钙碱性系列,少量为碱性系列。斑岩型矿床氧逸度δFMQ值变化于2~4之间,并普遍属于埃达克质岩,体现较好的成矿远景。斑岩带的形成造就NE向斑岩型成矿带产出,而NE向断裂带即是斑岩成矿构造,故亦可称之为斑岩型构造-岩浆-成矿带。NE向斑岩带的识别与确认,是东昆仑斑岩类地质与成矿研究的新发现,这对区内的构造活动、岩浆作用、地质演化与成矿预测等,均具重要意义。

In recent years, some porphyry bodies and ore deposits have been recognized and explored in Eastern Kunlun Mountains, indicating the importance of porphyry mineralization and ore prospecting potential of the regional porphyry deposits. This paper reports our recent discoveries of several new porphyry belts in the Eastern Kunlun Mountains. These porphyry belts of different scales occurred in parallel with the NE-trending. The belts not only distribute between but also cut across two main EW-trending regional faults. They occurred in the Southern, Middle and Northern Kunlun Blocks or across, cropping prominently in the Middle and Northern Blocks as well as in the Dulan and Qimantage areas of the east and west sections of the Eastern Kunlun Mountains, respectively. Granitic porphyry bodies mainly belong to the high potassium, calc-alkaline series, with occurrence of a few alkaline series~ they formed in the Indo-Chinese epoch while mineralization concentrated in the late Indo-Chinese epoch. The mineralizing porphyries are adakitic, with oxygen fugacity 8FMQ value ranges from 2 to 4, showing promising mineralization prospects. The occurrence of porphyry belts resulted in the formation of the NE-trending porphyry mineralization belts, which can also be called the tectonomagmatic controlled ore-forming belts as the NE-trending fault is part of the porphyry metallotectonics. It is a seminal achievement in porphyry geology and metallogenic study of the Eastern Kunlun Mountains that the NE porphyry belts were recognized and confirmed, which has profound significance in the exploration of magmatism, tectonic activity, geological evolution and metallogenic prognosis in the region.