PETROCHEMICAL STUDY OF THE CENOZOIC BASALTIC ROCKS IN EASTERN CHINA (PART 1 OF 2)

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Abstract
Cenozoic basalt lavas are widely distributed in the coastal region and adjacent districts in eastern China. They form either widespread plateaus or scattered mesas; and, in some places, the volcanic craters are well preserved. These basalt sheets were erupted from multiple vents in the late Tertiary and early Quaternary. The results of a petrochemical study of the Cenozoic basalt in eastern China are given. The most characteristic feature of the more basaltic rocks is their high K20 content, also the undersaturation in silica. In North China and South Manchuria most basalts are trachybasalts and occasional nepheline basalt. The constituent minerals of these basalts are anorthoclase, potashadesine, plagioclase, titanaugite, and abundant olivine. In South China the main basalt is olivine basalt, consisting of olivine, augite, and plagioclase. At some places the basalt may be slightly silica saturated and the occasional presence of hyperthene and quartz (xenocryst) is noteworthy. In North Manchuria the dominant basalt is leucite basalt, containing leucite and olivine as phenocryst and ground-mass constituents. Xenocrysts of quartz and feldspar are sometimes present. In Taiwan Province, the basalt of Kuan-yin-shan (volcano) is of the tholeiite type, but, in some other districts, the alkaline basalt with feldspathoidal constituent also occurs. The petrographical difference seems to be matched by the differences of the major tectonic forms of China. These facts are tabulated as follows: Table

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