摘要
本文论述了广西泥盆系火山岩特征及其分布特征,并探讨了与构造、矿产间关系。认为:泥盆纪广西地壳除钦州海槽外处于相对稳定的地台阶段,火山岩发育始自早泥盆世晚期塘丁时,至晚泥盆世最为强烈;主要受基底断裂或同沉积断裂控制的断陷带(台沟相)海底间隙性中基性火山活动产物,以层次多、厚度小为特点,组成玄武玢岩—粗面岩建造,它与硅泥质岩、碳酸盐岩建造共生,沿NW、NE向断裂作断续带状分布,有少许层状、透镜状玄武玢岩、粗面斑岩等次火山侵入相伴生,局部地段(龙州)在该两组断裂交汇处构成一套较厚的火山岩;在岩性上有由基性—中性向酸性演变,在时间上由点到面、由弱到强发展过程,在空间上由南而北、由西向东迁移趋势,可能为泥盆纪大陆边缘裂谷型钙碱性火山岩。还指出:广西境内丹池矿带锡多金属矿床、环江北山铅锌黄铁矿床、下雷与木圭锰矿等与泥盆系火山岩有关,提供了部分物质来源。
Devonian volcanic rocks and their distributive characteristics in Guangxi are dealt with in this paper,and the relationship between the volcanic rocks and the tectonics,mineral resources are also discussed. In Devonian period,the crust in Guangxi was in relative stable platformal stage except that Qinzhou geosyncline was in active time. Volcanic rocks were developed from Tangding Chron of Late early Devonian Epoch to Late Devonian Epoch, especially at Late Devonian Epoch. The volcanic rocks were the products of fissure intermediate-basic volcanism on fault-subsidence sea floor which is controlled by basement faults or synsedimentary faults. They are characterized by polybeds and small thickness and constitute basalt- porphyrite- trachyte formation which is intergrowthod with siliceous-rock,mudstone and carbonate rock formation. The volcanic formation occurs along NW-strike and NE-strike faults in the form of discontinuous belts, accompanied by such subvolcanic rocks as bedded and lensoid basalt porphyrite and trachyte porphyry and so on. At the intersection place of two groups of faults in local section (Longzhou for instance)thick-bedded formed. They e-volved from basic to intermediate to acid rock in rock property,from weakness to violenoe in degree, moved from south to north and from west to east in space. There may be continental marginal rift-type calcic-alkali volcanic rocks in Devonian period. It is painted out that tin-polymetallic deposit along Nandan-Hechi metallogenic belt, Beishan lead - zinc pyrite deposit, Xialei and Mugui manganese deposit in Guangxi are related to the volcanic rocks in Devonian period which provide some oreforming material.
