摘要
本队近年发现的沅陵—溆浦一带上震旦统火山碎屑岩,分布广泛,层位稳定。主要岩石类型有凝灰岩、沉凝灰岩及凝灰质页岩,具明显的变余凝灰结构和假流纹构造。化学成分具SiO^2高和K_2C>N_a2O的特点,在尼格里四面体图解中,其成分点分布于火成岩与粘土沉积岩界线附近。富含重稀土元素Y和Yb。与之共生的凝灰质沉积岩富含多种金属元素,是董家河式黄铁铅锌矿的重要矿源层。该区火山碎屑岩的发现对开展雪峰期—加里东期华南弧后盆地火山硅质页岩建造的研究和地质找矿具有一定的意义。
The recently-discovered Upper Sinian pyroclastic rocksin Yuanling-Xupu are distributed widely and are of steady stratigraphic horizon. The main rocktype includes tuff, tuffite and tuffaceous shale. They are of obvious palimpsest tuffaceous texture and pseudofluidal structure. Their chemical composition is characteristic of high SiO_2 content and K_2O>Na_2O, and in the Niggli's tetrahedron classification diagram, their composition points concentrates near the boundary between igneous rock and clay sedimentary rock, and rich in heavy rare earth element Y and Yb. The tuffaceous sedimentary rocks associated with them are rich in many kinds of metal element, which is considered to be an important source bed for Dongjiahe type lead-zinc-pyrite deposits. The discovery of pyroclastic rocks in this area is of significance for the geologic research on the volcanogenic siliceous shale sequence in the Southchina back-arc basin in the period between Xuefeng orogony and Caledonian orogeny and for geologic exploration.
出处
《湖南地质》
1990年第3期63-68,共6页
Hunan Geology
关键词
火山碎屑岩
晚震旦世
矿源层
Pyroclastic rock
Upper Siniau Series
Source bed of ore
Volcanogenic siliceous shale sequence
