西北地区重要金属矿产成矿特征及其找矿潜力

西北地区主要金属矿产种类繁多,大中型金属矿床309处。其地处大陆腹地,以塔里木陆块为主体,东接华北地台西段的阿拉善地块,南、北分别由众多微陆块镶嵌的显生宙造山系构成。北造山系以天山-兴安岭华力西造山系的西段为主体,向北接有阿尔泰-额尔古纳加里东造山系,间有准噶尔、伊犁等微地块。南造山系则自北向南依次由秦祁昆中央造山系中西段、松潘甘孜造山系等组成,间有中祁连、柴达木等微地块。构造复杂,是典型的陆内造山带发育地区。总体上处于古亚洲造山区,南接特提斯造山区,东叠环太平洋造山区。西北地区以元古宙-古生代金属成矿为显著特色。岩浆熔离型铜镍矿床、块状硫化物铜多金属矿床、海底喷流(气)型铅锌矿床、斑岩型铜钼矿床、矽卡岩型钨矿床及热液蚀变岩型金属矿床是主要的成矿类型。依据时空统一、区域地质构造和成矿演化,结合成矿理论分析,西北地区成矿单元划分主要处于3个成矿域:自北而南古亚洲成矿域、秦祁昆中央成矿域和特提斯成矿域。古亚洲成矿域主要由阿尔泰、西天山-西南天山、东天山、北山成矿带组成,夹持有准噶尔盆地和塔里木盆地,以晚古生代内生矿床产出为特点。秦祁昆中央成矿域以自西而东主要有西昆仑-阿尔金、祁连山、东昆仑、秦岭成矿带构成,祁连山、东昆仑之间夹持有柴达木盆地,以元古宙、早古生代内生矿床成矿为显著特点。特提斯成矿域仅出露于青海的南部,三江成矿区的北段以中新生代成矿为特点。已有的矿产资源资料和最新地质大调查专项工作进展表明,在西北地区广大的找矿空间和良好的成矿条件基础上,需重新认识成矿地质背景,科学地确定主攻方向,以新发现的十余处具有大型-超大型金属矿床潜力的远景区为勘查重点,集中攻关,加强综合性研究,实现地质找矿重大突破。

Metallogenetic Characteristics and Prospecting Potential of Major Metallic Minerals in Northwest China

Northwest China has abundant mineral resources with 309 large-, medium-size metallic ore deposits found. As centered by the Tarim block, the region connects with the Alashan massif situated on the northwestern margin of the North China craton to its east, while to the north and south, there are the Phanerozoic orogenic systems consisting of numerous microblocks. The orogenic system to north is represented by the Hercynian Tianshan-Hinggan orogen that connects the Caledonian Altay-Ergun orogen with sandwich of the Junggar and lli massifs in between. The southern orogenic system is composed of the central and western Qinling-Qilian-Kunlun and Songpan-Ganzi orogens from north to south, with the middle Qilian and Qaidam massifs. The region belongs to a complex intracontinental orogenic belt. As a whole, northwest China is surrounded by the Paleo-Asian orogenic belt, the Tethyan orogenic belt and by the circum pacific orogenic zone to its north, south and east, respectively. The Proterozoic and Palaeozoic are two main metallogenic periods in the region. The main metallogenic types are magma liquation Cu and Ni deposits, massive sulphide Cu and polymetallic deposits, sea floor exhalation Pb and Zn deposits, porphyry Cu and Mo deposits, skarn W deposits and hydrothermal alteration metallic deposits. According to regional geology and metallogenic evolution, we divided the metallogenic unit in northwest China into 3 ore-forming domains, from north to south, they are: the Paleo-Asian metallogenic domain, the Qinling-Qilian-Kunlun metallogenic domain and Tethyan metallogenicdomain. The Paleo-Asian metallogenic domain is made up of Altay, west-southwest Tianshan, east Tianshan and Beishan metallogenic belts with the Junggar and Tarim basins, characterized by late Paleozoic endogenic mineralization. The Qinling-Qilian-Kunlun metallogenic domain contains west Kunlun-Altyn Tagh, Qilian, east Kunlun and Qinling metallogenic belts having the Qaidam basin inside, featured by Proterozoic and early Paleozoic mineralization. The Tethyan metallogenic domain consists mainly of north Sanjiang metallogenic belt located in southeast Qinghai-Tibet plateau, with middle Cenozoic being the major metallogenic period. Existing evidence and new development of the mineral resource investigation indicate that northwest China possesses favorable metallogenic conditions and a great potential for further prospecting work. We have to re-study the geological and metallogenic background and focus on key exploration work over 10 potential large-and super large-size metallic ore-forming areas in order to have great breakthroughs in prospecting.