摘要
北祁连造山前的构造聚敛样式的诸多争议 ,主要源于北祁连山东西段的巨大差异。甘肃肃南白泉门以东主要表现为 ,自北而南发育有弧后、岛弧和洋中脊、洋岛海相火山岩系 ,产出岛弧裂谷白银厂式 (黑矿型 )和弧后扩张脊石居里沟式 (塞浦路斯型 )块状硫化物矿床 ,少见陆壳基底碎块 ,花岗岩侵入体不发育 ;而西段以镜铁山微地块为特点 ,岛弧钙碱性火山岩系发育 ,分布有大面积花岗质岩基 ,产出夕卡岩型钨矿床。这种东西段区域岩石组合和成矿特征上的差异 ,反映了早古生代北祁连洋盆在中奥陶世—早志留世向北俯冲消减构造聚敛上的不同 ,东段为洋—洋俯冲的马里亚纳型的沟—弧—盆系大陆边缘 ,西段则转换为洋—陆俯冲的智利型活动大陆边缘 ,并由于深部消减物质的差异而形成不同的碰撞岩浆作用形式和相应的成矿组合。
Various dispute referring to the types of pro-orogenic convergence patterns in the North Qilian mainly come from the very large differences between west part and middle—east part of the North Qilian. East of Baiquanmen, Gansu, it shows that from north to south there are three sets of back-arc, island-arc and oceanic-ridge and oceanic-island volcanic rocks, in which the Baiyinchang island-rift (Kuroko type) and back-arc spreading ridge (Cyprus type) massive sulfide deposits had been found, with fragments of continental basements and granitic intrusions rarely seen. But the west part is characterized by the Jingtieshan micro-block, with well-developed island-arc calc-alkaline volcanic rocks and a large area of granitic batholiths, and skarn-type tungsten ore deposits have been found. These differences between the east and west parts in regional rock assemblages and metallogenic characteristics reflect the differences in tectonic convergence of the Early Paleozoic North Qilian oceanic basin during the Middle Ordovician—Early Silurian subduction to the north. The east part was a continental margin of trench—arc—basin system related to an ocean—ocean collision, but the west part was transformed to an active continental margin related to an ocean—continent collision. Also, owing to the differences of deep-seated subduction materials, various collision magmatism processes and corresponding metallogenic assemblages have been formed.
出处
《地质论评》
CAS
CSCD
北大核心
2005年第2期120-127,共8页
Geological Review
基金
国土资源部矿产资源补偿费资助的矿产勘查项目 (编号 2 0 0 2 -0 3 )的成果。
