| 我国东部新生代玄武岩岩石化学的一些探讨 |
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| 引用本文： | 郑学正
,从柏林
,张雯华
,严正.我国东部新生代玄武岩岩石化学的一些探讨[J].地质科学,1978,13(3):253-264. |
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| 作者姓名： | 郑学正 从柏林 张雯华 严正 |
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| 摘 要： | 新生代是地球上玄武质岩浆的主要活动期。在我国东部,新生代玄武岩分布也极广泛,由北往南自大兴安岭、松辽盆地经华北、苏闽浙至台湾、海南岛以及近海大陆架均有不同程度的出露。时间上从老第三纪至史期均有玄武岩喷发活动。
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| 关 键 词： | , |
DISCUSSION ON THE PETROCHEMISTRY OF CENOZOIC BASALTIC ROCKS IN EASTERN CHINA |
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| Zheng Xuezheng,Cong Bolin,Zhang Wenhua,Yan Zheng.DISCUSSION ON THE PETROCHEMISTRY OF CENOZOIC BASALTIC ROCKS IN EASTERN CHINA[J].Chinese Journal of Geology,1978,13(3):253-264. |
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| Authors: | Zheng Xuezheng Cong Bolin Zhang Wenhua Yan Zheng |
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| Abstract: | In this paper sixty five new chemical analyses and six K-Ar age-data of basalts from Eastern China are presented. In Eastern China there are two types of Tertiary basalts. The first is referred to by the writers as a new type of basalt and named "transitional tholeiitic basalt", occurring mainly under the North China Plain, while the other is alkalic basalt (and minor amount of tholeiitic basalt) found nearby the deep faults.The former is characterized predomintly by the Ca- and Al-poor, higher Mg/Ca value, slightly high alkali and slight undersaturation or saturation in silica: these characters are also reflected more or less in alkali basalts of this region. It is thus clear that the two types of basalts have generated under similar conditions from primary basaltic magma. According to the petrochemical study of basalts and xenoliths in basalts from this region it is suggested that the transitional tholeiitic basalts may be fromed by partial melting at a depth about 35 to 50 km, i.e., between the basal part of the stable plagioclase-iherzolite zone and the upper part of spinel-iherzolite zone in the upper mantle, whereas the alkali basalts may have been formed at a depth of about 50-60km within the stable spinel-iherzolite zone of the upper mantle. From its petrochemical features, i.e. Ca- and Al-poor and Mg/Ca value high, the two types of basalts seem to be erupted rapidly from the source region of primary basalts, due to the week assimilation and differentiation at low pressure. Clearly, the spatial distribution and the chemical composition of basalts are all controlled by plate tectonics.Based on the model of plate tectonics, the pattern of material convection within the Earth may be assumed as follows: the convection current of mantle material turns upwards, while the crust material enters the mantle and subduces along the Benioff zone. Thus the main pattern of movement of the Earth’s material is that the high density material moves upwards and the light density one moves downwards, which distinctly contradicts with the law of gravitation and physico-chemistry. In fact, such an unusual movement of the Earth’s material is present merely locally and on a small scale. According to the pattern of plate tectonics the rotation of Earth and its material equilibrium could be upset. But the distribution of basalts in the continent is chiefly controlled by faults, which cause either expansion fiving rise to the abrupt reduction in pressure or compression inducing the increase in temperature. In the latter ease faults will cause a partial melting of the upper mantle substance, resulting in the generation of primary basaltic magma with various compositions. |
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