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长白山天池火山是典型的大陆板内碱性火山,岩石组合以玄武岩盾和粗面岩、碱流岩等碱性岩为主。为厘清天池火山粗面岩的形成过程,本文在综合前人研究的基础上,结合本文新发表数据,检验了粗面岩的成因。研究结果显示天池火山粗面岩不可能由古老的华北克拉通下地壳部分熔融形成,也不符合造盾玄武岩部分熔融的模式。通过主量元素、微量元素定性和定量计算后认为粗面岩是由进化玄武质岩浆(玄武粗安岩)经历了分离结晶作用所形成,粗面岩形成过程中岩浆遭受了地壳混染,并且具有高n(~(87)Sr)/n(~(86)Sr)和低n(~(87)Sr)/n(~(86)Sr)两种截然不同的混染趋势。结合岩相和层序信息,作者认为两种演化趋势是上地壳岩浆房系统变化的反映。早期玄武质岩(头道白山期)上侵至上地壳演化,因与上地壳直接接触,沿高n(~(87)Sr)/n(~(86)Sr)趋势演化。随着岩浆房接受补给,岩浆房逐渐增大,新侵入的岩浆与地壳被早期岩浆房结晶形成的岩浆房壁所隔挡,使得年轻粗面岩和碱流岩只与早期粗面质岩浆的残留体等进行物质交换,最终沿着低Sr同位素比值趋势演化。
The Changbaishan Tianchi volcano is a typical alkaline volcanic in the continental plate. The rock assemblage is mainly composed of basaltic rocks such as basaltic rock, crude rock and alkali flow rock. In order to clarify the formation process of the volcanic trachyte in Tianchi, based on the previous studies and combined with the newly published data in this paper, the paper tests the genesis of the trachyte. The results show that the Tianchi volcanic facies can not be formed by the partial melting of the lower crust of the ancient North China Craton, nor does it conform to the partial melting mode of the basalt. Through qualitative and quantitative calculation of major elements and trace elements, the authors believe that the facies formed by the evolution crystallization of basaltic magmas (basaltic sorbite), and the magmas suffered crustal contamination during the formation of the facies There are two distinct mixed trends of high n (~ (87) Sr) / n (~ (86) Sr) and low n (~ (87) Sr) / n (~ (86) Sr) Combining the lithofacies and sequence information, the authors consider that both evolutionary trends are a reflection of the changes in the upper crustal magma chamber system. The evolution of the upper basalts from the early basaltic rocks (Huodou Baishan period) to the upper crust evolves along the high n (~ (87) Sr) / n (~ (86) Sr) because of direct contact with the upper crust. With the replenishment of the magma chamber, the magma chamber was gradually increased, and the newly intruded magma and crust were separated by the magmatic chamber wall formed by the early magma chamber crystallization, so that the young trachyte and alkali flow rock were only associated with the early rough magma Residual matter and other material exchange, and ultimately along the low Sr isotope ratio trend evolution.