广东玄武质火山岩中超基性岩角砾地质特征

GEOLOGIC FEATURES OF ULTRABASIC BRECCIAIN BASALTIC VOLCANICS, GUANGDONGPROVINCE, SOUTH CHINA

In this paper the geologic features of ultrabasic breccia occurring in basaltic volcanics at Qilin, Jilongshan, Tianyang, Qingtongyang, Penglai, etc., Guangdong province, South China, have been reported and the mode of occurrence, litholegy and mineralogy of it and its host rocks described as well. On this basis, the author has hoeld out his arguments below: It is pointed out that the ultrabasic breccia referred to in the present paper,commonly called ultrabasic inclusion or nodule, occurs not only in basaltic lavas, but also, to a greater extent, in basaltic pyroclastic rocks. Its geologic features lead us to believe that the breccia was, in solid state, derived from the upper mantle. It is postulated from its distribution pattern that strong fault activities took place along the seashore areas of Guangdong during the middle Quarternary, followed by the eruption of basaltic magma which contributed significantly to the bringing out of the ultrabasic breccia. Geological evidenee shows that the ultrabasic breccia occurs in the NW trending secondary tension fault zone rather than in the major fault zone, though controlled by the Neocathaysian structural system. At the same time, the author has considered the crustal structure at depth in eastern Guangdong, the Leizhou Peninsular and the Hainan Island, on the ground of the differences in the composition of breccia from different areas and. presented his own opinions. It is concluded from the breccia types that the faults developed at Qilin, eastern Guangdong, would probably cut into the upper mantle more deeply respective to those in the Leiqiong area,South China.

In this paper the geologic features of ultrabasie breccia occurring in basaltic volcanics at Qilin, Jilongshan, Tianyang, Qingtongyang, Penglai, etc., Guangdong province, South China, have been reported and the mode of occurrence, lithology and mineralogy of it and its host rocks described as well. On this basis, the author has held out his arguments below:It is pointed out that the ultrabasie breccia referred to in the present paper, commonly called ultrabasie inclusion or nodule, occurs not only in basaltic lavas, but also, to a greater extent, in basaltic pyroclastic rocks. Its geologic features lead us to believe that the breccia was, in solid state, derived from the upper mantle. It is postulated from its distribution pattern that strong fault activities took place along the seashore areas of Guangdong during the middle Quarternary, followed by the eruption of basaltic magma which contributed significantly to the bringing out of the ultrabasie breccia. Geological evidence shows that the ultrabasie breccia occurs in the NW trending secondary tension fault zone rather than in the major fault zone, though controlled by the Neocathaysian structural system. At the same time, the author has considered the crustal structure at depth in eastern Guangdong, the Leizhou Peninsular and the Hainan Island, on the ground of the differences in the composition of breccia from different areas and presented his own opinions. It is concluded from the breccia types that the faults developed at Qilin, eastern Guangdong, would probably cut into the upper mantle more deeply respective to those in the Leiqiong area, South China.