摘要
葫芦河群系分布在甘肃东部,从原“牛头河群”中分解出来的早古生代岩系。依据先后发现的生物化石和最近取得的同位素年代学数据,可划分为寒武系、奥陶系和志留系的地层单元。本文为对其火山岩岩石学的研究报导,文中论述了岩系中拉斑质枕状玄武岩(蛇绿岩套)和钙碱质火山岩的岛弧火山组合特征,并研讨了北秦岭与北祁连造山带间的构造衔接与成矿关系。
A. series of barren metamorphic rocks ocurring along the Niutou River and on the Shaanxi-Gansu border is called the 'Niutouhe Group'. Some geologists assign it to the Precambrian, while others, to the Early Paleozoic.The authors studied this series during 1988 to 1989 and obtained some new information. They consider that the Niutouhe Group includes: (1) Precambrian metamorphic rock series of the Longshan Group, (2)Early Paleozoic metamorphic rock series of the Huluhe Group, and(3)Precambrian metamorphic rock series of the Qinling Group. This paper discusses the volcanic rocks of the disintegrated Huluhe Group composed of Cambrian, Ordovician and Silurian low-grade metamorphic rock series and the relations of regional tectonics and mineralization between the Qinling and North Qilian orogens; besides it also reports some new data on the stratigraphic paleotology and isotope chronology.The authors think that the Huluhe Group links the Qinling and North Qilian orogens. The volcanic rocks are represented by an association of tholeiitic and calc-alkaline volcanic rocks. In the light of the theory of plate tectonics, this volcanic association is interpreted as the product of volcanic arc or marginal-sea volcanism.Some volcanogenic massive sulfide ore deposits occur in volcanic strata of the Huluhe Group and its neighbouring areas. According to the ore lead ages of these deposits and Rb-Sr ages of host rocks, their mineralization ages exhibit a very narrow range from 377 to 500 Ma, which are consistent with the Tremadocian to Arenigian metallogenic stages. These data indicate that the mineralization times of these deposits are paracontemporaneous.Thus it seems that they have the timebound and strata-bound nature.
出处
《地质论评》
CAS
CSCD
北大核心
1991年第3期221-234,共14页
Geological Review
基金
地质科学技术行业基金(编号88018)
