青海“三稀”矿床成矿系列、成矿规律与找矿方向

Metallogenic Series,Metallogenic Regularity,and Prospecting Direction of Rare Earth,Rare Metal,and Rare-scattered Minerals in Qinghai Province

青海“三稀”矿以稀有金属矿产和伴生稀散元素矿产为主,稀土矿床分布于拉脊山成矿带和柴北缘成矿带,类型仅有岩浆型(轻稀土)和岩浆热液型(轻稀土),成矿于早古生代奥陶纪和志留纪,成矿环境研究程度较低。稀有金属矿床主要出露于西秦岭成矿带和柴达木成矿带,类型可分为与岩浆作用有关的岩浆型(铌、钽)、伟晶岩型(锂、铍、铌、钽)、岩浆热液型(铌、钽);与沉积作用有关的蒸发沉积型(锂)和化学沉积型(锶),岩浆作用矿床成矿高峰期为中生代三叠纪,成矿于古特提斯演化后碰撞环境,沉积作用矿床成矿爆发期为新生代新近纪和第四纪,与青藏高原强烈抬升所致的断陷成盆及干旱气候有关;稀散元素矿床均为有色金属矿床的伴生矿,广泛分布于北祁连成矿带、柴北缘成矿带、东昆仑成矿带、西秦岭成矿带和阿尼玛卿成矿带,矿种多样,已知成矿元素有Ga、Ge、Cd、In、Se、Te等,矿床类型丰富,主要包括海相火山岩型、接触交代型和陆相火山岩型,成矿时代相对集中于早古生代奥陶纪、晚古生代二叠纪和中生代三叠纪,可能形成于原特提斯演化弧后盆地、岩浆弧环境。依据矿床时空分布特征、成矿作用及成矿地质背景,将青海“三稀”矿产划分为10个矿床成矿系列、18个矿床成矿亚系列、20个矿床式。基于“三稀”矿床区域成矿地质背景、区域成矿条件、已知矿化信息和研究程度分析,提出了成矿区带不同类型“三稀”矿产找矿远景,认为西秦岭成矿带、柴北缘成矿带和东昆仑成矿带为伟晶岩型锂、铍、铌、钽、铷稀有金属找矿远景区,柴达木成矿带为蒸发沉积型和化学沉积型锂、锶、铷矿找矿远景区;对于研究程度较弱的稀散元素矿,除在已知的矿集区着力稀散元素赋存状态、超常富集研究和资源量核算之外,东昆仑成矿带牛苦头—野马泉矽卡岩型有色金属矿集区为稀散元素找矿的有利远景区。

The rare earth,rare metal,and rare-scattered mineral deposits in Qinghai are dominated by rare metal minerals and associated rare and scattered element minerals.Rare earth deposits are distributed in the Lajishan metallogenic belt and the metallogenic belt in the northern margin of Qaidam Basin.Only magmatic(light rare earth)and magmatic hydrothermal(light rare earth)types are present here.Mineralization occurred in the early Paleozoic during the Ordovician and Silurian,and research on the metallogenic environment of the region is limited.Rare metal deposits are mainly exposed in the West Qinling metallogenic belt and Qaidam metallogenic belt,and can be divided into magmatic type(Nb,Ta),pegmatite type(Li,Be,Nb,Ta)and magmatic hydrothermal type(Nb,Ta)in terms of magmatism,and evaporation deposition type(lithium)and chemical deposition type(strontium)in terms of sedimentation.The mineralization of magmatic deposits peaked in the Triassic during the Mesozoic era,originating in the collision environment after the evolution of the Paleo-Tethys.The metallogenic explosion period of sedimentary deposits occurred during the Neogene and Quaternary of the Cenozoic era,and is related to faulted basin formation and arid climate caused by the strong uplift of the Qinghai-Tibet Plateau.Rare and scattered element deposits are associated with non-ferrous metal deposits,which are widely distributed in the North Qilian metallogenic belt,the northern Qaidam metallogenic belt,the East Kunlun metallogenic belt,the West Qinling metallogenic belt and the Animaqing metallogenic belt,and comprise various minerals.The known metallogenic elements are Ga,Ge,Cd,In,Se,Te,et.The types of deposits are rich,mainly including marine volcanic rock type,contact metasomatic type,and continental volcanic rock type.The metallogenic age is concentrated in the early Paleozoic(Ordovician),late Paleozoic(Permian),and Mesozoic(Triassic),which may have formed in the back arc basin and magmatic arc environment during the evolution of the original Tethys.Based on the temporal and spatial distribution characteristics of deposits,mineralization,and metallogenic geological background,the rare earth,rare metal,and rare-scattered minerals in Qinghai are divided into 10 metallogenic series,18 metallogenic subseries,and 20 metallogenic types.Based on the analysis of the regional metallogenic geological background,regional metallogenic conditions,known mineralization information,and research of the rare earth,rare metal,and rare-scattered minerals deposits,the prospecting prospects of different types of rare earth,rare metal,and rare-scattered mineral deposits in the metallogenic belt are put forward.The western Qinling metallogenic belt,northern Qaidam metallogenic belt,and eastern Kunlun metallogenic belt are considered to be prospecting areas for pegmatite lithium,beryllium,niobium,tantalum,rubidium.The Qaidam metallogenic belt is of evaporative deposition type with a chemical deposition of lithium and strontium,and is a prospecting area for rubidium ore.For poorly studied rare and scattered element deposits,in addition to focusing on the occurrence state of rare and scattered elements,abnormal enrichment research and resource accounting is necessary in the known ore concentration areas in the Niukutou Yemaquan skarn type nonferrous metal ore concentration area.The eastern Kunlun metallogenic belt is a favorable area for rare and scattered element prospecting.