青海省柴北缘成矿带矿床成矿系列

Metallogenic Series of Deposits in the Northern Qaidam Metallogenic Belt of Qinghai Province,China

青海省柴北缘成矿带成矿条件优越,是仅次于东昆仑成矿带的国家重要矿产资源接续地。成矿带内金、铅、锌、煤、石棉、石灰岩、硼等重要矿种主要分布于滩间山岩浆弧(Ⅳ24-2锡铁山—布果特山Pb-Zn-Au-Cu-Mn-煤-盐类成矿亚带)、欧龙布鲁克地块(Ⅳ24-3大煤沟煤-U-黏土成矿亚带)和柴北缘蛇绿混杂岩带(Ⅳ24-5绿梁山—阿尔茨托山Pb-Zn-Au-Mn-Cr-Fe-W-稀有金属-金红石-石灰岩-黏土成矿亚带)。矿产资源在空间展布上表现出滩间山岩浆弧产出以岩浆热液型青龙沟式金矿床和海相火山岩型锡铁山式铅锌(银)矿床为代表,而柴北缘蛇绿混杂岩带则赋存与印支期中酸性侵入岩有关的接触交代型多金属矿床为主的特点。伴随着前南华纪(2.50~0.78 Ga)结晶基底形成、南华纪—泥盆纪(780.0~359.6 Ma)大陆裂解-碰撞造山、石炭纪—三叠纪(359.6~199.6 Ma)古特提斯洋演化、侏罗纪—白垩纪(199.6~65.5 Ma)陆内演化和新生代(65.5~0 Ma)高原隆升的成矿地质构造环境演化,形成以海相火山岩型铅、锌、锰,岩浆型铬,受变质型石英岩等为主的内生矿床,以生物化学沉积型煤、化学沉积型石灰岩、蒸发沉积型盐湖等为主的外生矿床。研究区53个矿种的成因类型主要属于岩浆作用矿床与沉积作用矿床,成矿期以早古生代和中生代为主,次为晚古生代和第四纪。以柴北缘地区地质构造演化与成矿时空特点为基础,依据成矿系列理论,共厘定出柴北缘成矿带矿床成矿系列组15个、矿床成矿系列20个、矿床成矿亚系列16个、矿床式23个。在讨论早古生代和早中生代重大构造活动与关键成矿事件的关系基础上,从区域地质演化角度探讨了构造对成矿的约束,认为构造环境控制矿床类型、矿种和成矿强度。

The northern Qaidam metallogenic belt in Qinghai province has superior metallogenic conditions,and is the continuation of national important mineral resources only second to East Kunlun metallogenic belt.Gold,lead,zinc,coal,asbestos,limestone,boron and other important minerals in the metallogenic belt are mainly distributed in Tanjianshan magmatic arc(Ⅳ24-2 Xitieshan-Buguoteshan Pb-Zn-Au-Cu-Mn-coal-salt metallogenic sub-belt),Oulongbrooke block(Ⅳ24-3 Dameigou Coal-U-clay metallogenic sub-belt)and the ophiolitic melange belt in the northern margin of Qaidam Basin(Ⅳ24-5 Luliangshan-A ercituoshan Pb-Zn-Au-Mn-Cr-Fe-W-rare metal-rutile-limestone-clay metallogenic sub-belt).The spatial distribution of mineral resources shows that the occurrence of Tanjianshan magmatic arc is represented by magmatic hydrothermal Qinglonggou-type Au deposit and marine volcanic Xitieshan-type Pb-Zn deposit,while the ophiolitic melange belt in the northern margin of Qaidam Basin is mainly characterized by contact metasomatic polymetallic deposits related to Indosinian intermediate acid intrusive rocks.With crystalline basement in Pre-Nanhua Period(2.50-0.78 Ga),continental breakup collision orogeny in Nanhua Period-Devonian(780.0-359.6 Ma),Paleotethyan ocean evolution in Carboniferous-Triassic(359.6-199.6 Ma),intracontinental evolution in Jurassic-Cretaceous(199.6-65.5 Ma)and plateau uplift in Cenozoic(65.5-0 Ma),the evolution of metallogenic geological structure environment has formed endogenetic minerals dominated by marine volcanic rock type of Pb,Zn and Mn,and magmatic chromium and metamorphic type of quartzite,and exogenous minerals dominated by biochemical sedimentary type of coal,chemical sedimentary type of limestone and evaporative sedimentary type of salt lake.The genetic types of 53 minerals in the study area mainly belong to the deposits with magmatism and sedimentation,and the metallogenic epochs are mainly Early Paleozoic and Mesozoic,and secondly Late Paleozoic and Quaternary.Based on the geological tectonic evolution and metallogenic temporal-spatial characteristics,according to the theory of metallogenic series,15 metallogenic series groups,20 metallogenic series,16 metallogenic sub-series and 23 metallogenic types in the northern margin of Qaidam Basin were determined.The relationship between major tectonic activities and key metallogenic events in Early Paleozoic and Early Mesozoic was analyzed,and the constraints of structure on mineralization from the perspective of regional geological evolution were discussed.It is considered that the structural environment controls the types of deposits and metallogenesis intensity.