昆仑古特提斯构造转换与镍钴锰锂关键矿产成矿作用研究

Tectonic transformation of the Kunlun Paleo-Tethyan orogenic belt and related mineralization of critical mineral resources of nickel,cobalt,manganese and lithium

【研究目的】特提斯构造域研究愈来愈显示为原特提斯、古特提斯和新特提斯三分的特点,其中古特提斯洋的形成演化及其成矿作用的研究较为薄弱。【研究方法】本文根据东昆仑夏日哈木早泥盆世超大型镍钴硫化物矿床、帕米尔玛尔坎苏晚石炭世大型火山源沉积型富锰矿和西昆仑大红柳滩晚三叠世大型伟晶岩型锂铍矿床发现事实,将它们成矿的构造地质背景演化作为主线关联起来研究,提出它们分别代表了古特提斯裂解、大洋扩张和闭合后碰撞构造转换结果的认识。【研究结果】认为与古亚洲洋同期的原特提斯洋于志留纪末碰撞闭合后,在冈瓦纳大陆北缘由于地幔柱作用改造的软流圈发生部分熔融而裂解,形成了以夏日哈木与裂解背景幔源镁铁—超镁铁岩有关的超大型岩浆镍钴硫化物矿床;随着进一步扩张,在早石炭世形成了古特提斯成熟大洋,由于大洋中脊喷发提供的成矿物质,在晚石炭纪随着大洋快速扩张向消减的转换,洋底碳酸盐岩沉积中形成了玛尔坎苏大型富菱锰矿矿床;古特提斯洋闭合后于中三叠世进入碰撞造山阶段,于晚三叠世后碰撞阶段地壳重熔形成的S型花岗岩高温热液流体,并造就了大红柳滩大型伟晶岩型锂铍矿床。早晚古生代之交是古特提斯洋裂解的开始,此时秦祁昆洋为代表的原特提斯主洋已经闭合,作为原特提斯洋弧后盆地的古亚洲洋尽管尚未闭合,但夏日哈木镍钴矿床则是原特提斯造山后陆壳再次裂解的产物,并非形成于原特提斯洋岛弧或后碰撞的环境;锰是亲石元素,岩浆作用中不富集,而在外生沉积作用中富集,说明古特提斯早石炭世新生洋壳是富锰的,淋滤出的锰离子在晚石炭世相对宁静洋底深处碱性环境中形成沉积型碳酸锰矿,代表了较为强烈的岩浆作用阶段向相对宁静的沉积环境的转换;大红柳滩S型花岗岩基及其大规模伟晶岩型锂铍矿的产出,则反映了强烈的碰撞造山作用导致的地壳重熔的地球动力学背景,应是古特提斯洋缝合造山后或后碰撞伸展的环境。【结论】就已有的成矿事实,东昆仑康西瓦—阿尼玛卿古特提斯缝合带与南部巴颜喀拉的西金乌兰—金沙江和羌塘的龙木错—双湖古特提斯缝合带相比,更富有地质意义。

This paper is the result of the mineral exploration engineering.[Objective]There are increasing evidences show that the Tethys tectonic domain can be divided into three stages of the Proto-Tethys,the Paleo-Tethys and the Neo-Tethys,among which the research on the formation and evolution of the Paleo-Tethys Ocean and related mineralization are relatively weak.[Methods]On the basis of the discovery of the Early Devonian Xiarihamu super-large nickel-cobalt sulfide deposit in the East Kunlun,the Late Carboniferous Malkansu large volcanic source sedimentary type manganese-rich deposit in the Pamir and the late Triassic Dahongliutan large pegmatite type lithium-beryllium deposit in the West Kunlun,this study focuses on the formation environment and tectonic evolution as the main line to find out their connection.It is proposed that the three large ore deposits represent the products of the tectonic transformation of Paleo-Tethys break,ocean expansion and ocean closure to continental collision,respectively.[Results]It is believed that after the closure of the Proto-Tethys ocean and continental collision,which was contemporaneous with the Paleo-Asian ocean at the end of the Silurian,the modified asthenosphere was partially melted and the northern margin of Gondwana continent breakup due to the mantle plume activity,forming the Xiarihamu super-large magmatic nickel-cobalt sulfide deposit related to the mantle-derived mafic-ultramafic rocks.With the further expansion of the Paleo-Tethys Ocean,the mature ocean was formed in the Early Carboniferous.In the Late Carboniferous,with transformation from rapid expansion to ocean subduction,the Malkansu large rhodochrosite-rich deposit was formed in the carbonate sedimentary of the ocean floor due to the ore forming material provided by the eruption of the mid-ocean ridge.After the closure of the Paleo-Tethys Ocean,it entered the collision orogenic stage in the Middle Triassic.In the Late Triassic post-collisional stage,high temperature hydrothermal fluid of S-type granite formed by the crust remelting,which lead to the formation of Dahongliutan large pegmatite-type lithium-beryllium deposit.The Early Paleozoic and Late Paleozoic alternation was the beginning of the Paleo-Tethys Ocean breakup.At this time the Qinling-Qilian-Kunlun Ocean as the representative of the Proto-Tethys Ocean has closed.Although the Paleo-Asian Ocean as a back-arc basin of the Proto-Tethys has not closed yet,the Xiarihamu nickel-cobalt deposit is the product of the re-cracking of continental crust after the Proto-Tethys orogeny,and it’s not formed in the environment of the Proto-Tethys island arc or post-collision.Manganese is a lithophilic element,which is not enriched in magmatism.However,it enriched in exogenous deposition,which indicates that the new oceanic crust of the Early Carboniferous of Paleo-Tethys is rich in manganese,and the leached manganese ions formed sedimentary manganese carbonate in the alkaline environment of relatively quiet ocean floor in the Late Carboniferous,which represents the transition from a strong magmatism stage to a relatively quiet sedimentary environment.In the Dahongliutan,the distribution of S-type granitic batholith and its large-scale pegmatite-type lithium-beryllium ore deposit reflect the geodynamic background of crust remelting caused by strong collisional orogeny.Therefore,it’s suggested the formation environment is post-orogeny or post-collision extension of the Paleo-Tethys.[Conclusions]As far as the existing facts of mineralization concerned,the Kangxiwa-Animaqing Paleo-Tethys suture zone in East Kunlun is of more geological significance than that of the Xijinwulan-Jinshajajiang in the southern Bayankara and the Longmuco-Shuanghu Paleo-Tethys suture zone in the Qiangtang.