青藏高原中东部1∶100万区域重力调查及成果

1∶1 000 000 REGIONAL GRAVITY SURVEY IN CENTRAL AND EASTERN QINGHAI-TIBET PLATEAU AND THE RESULTS OBTAINED

经对青藏高原中东部1∶100万区域重力资料的解释,编制了一批重力基础图和解释成果图。新划出嘉黎下地壳熔融区、拉萨下地壳隆起、乌兰乌拉—杂多古生代隆起带、唐古拉燕山期岩浆弧以及南冈底斯燕山—喜马拉雅期岩浆弧等构造单元;支持将班公错—怒江结合带作为冈瓦纳北界的认识;划出断裂逾百条、中酸性岩浆岩带多处,其中唐古拉岩浆岩带对羌塘盆地油气的储藏不利;冈底斯北部—可可西里中下地壳普遍存在熔融层;高原地壳存在着与重力均衡调整力相反的强大构造应力。这些认识对进一步研究青藏高原的地质构造、寻找与岩浆岩有关的多金属矿产等提供了依据。

The authors constructed a series of gravity base maps and interpretation maps on the basis of interpretation of the 1： 1 000 000 regional gravity data from central-eastern Qinghai-Tibet plateau. Some new tectonic units were delineated, such as Jiali lower crust melt zone, Lhasa lower crust uplift, Wulawula-Zaduo Paleozoic uplift zone, Tanggula Yanshanian magamtic arcs, and South Gangdise Yanshanian-Himalayan magamtic arcs. The authors support the opinion that Bangongcuo-Nujiang juncture zone should serve as the northern boundary of the Gangdise Mountain. Over 100 faults and many zones of intermediate-acidic magamtic rocks were recognized, in which the Tanggula magamtic belt is unfavorable to petroleum accumulation in Qiangtang basin. It is also concluded that there are widespread igneous layers beneath the middle-lower crust in northern Gangdise-Kekexili and there also exist very strong tectonic stress opposite to the adjusting power of the gravity balance in the plateau crust. All of these conclusions provide evidence for further study of geological tectonics in Qinghai-Tibet plateau and contribute to the search for polymetallic deposits related to magmatic rocks.