2024年1月23日，中国科学院地球化学研究所唐红峰及其团队成员在《地球化学学报》杂志发表论文，报道了他们在对碱性玄武岩质熔体与斜方辉石反应的实验研究中取得的新成果。

研究人员称，实验的起始熔体采样于辽宁阜新地区的碱性玄武岩，斜方辉石采样于河北大马坪地区的地幔捕虏体。实验结果表明，在所研究的P-T条件下，碱性玄武岩质熔体与斜方辉石的反应均形成单斜辉石。反应区中单斜辉石的形成主要受溶解—结晶控制，反应熔体的化学成分主要受扩散效应的影响。温度是控制熔体与斜方辉石反应的最重要的参数，它直接影响到斜方辉石的熔融和熔体中化学成分的扩散。温度还直接控制着反应区和反应熔体中新形成的单斜辉石的化学组成。

碱性玄武岩质熔体与斜方辉石反应生成单斜辉石，可使含该矿物的岩石中CaO和Al₂O₃含量增加。因此，软流圈地幔的碱性玄武岩质熔体与岩石圈地幔的斜方辉石的相互作用，可能导致华北克拉通岩石圈地幔由难熔向富质演化，并具有较高的CaO和Al₂O₃。此外，在某些熔融过程中，反应后的熔体经由初始的碱性玄武岩转化为拉斑玄武岩，表明拉斑玄武岩岩浆可能是由碱性玄武岩与斜方辉石反应生成的。

附：英文原文

Title: Experimental study on reactions between alkaline basaltic melt and orthopyroxenes: constraints on the evolution of lithospheric mantle in the North China Craton

Author: He, Hanqi, Wang, Mingliang, Tang, Hongfeng

Issue&Volume: 2024-01-23

Abstract: The experimental results of the reactions between an alkaline basaltic melt and mantle orthopyroxenes under high-temperature and high-pressure conditions of 1300–1400 °C and 2.0–3.0 GPa using a six-anvil apparatus are reported in this paper. The reactions are proposed to simulate the interactions between melts from the asthenospheric mantle and the lithospheric mantle. The starting melt in the experiments was made from the alkaline basalt occurring in Fuxin, Liaoning Province, and the orthopyroxenes were separated from the mantle xenoliths in Damaping, Hebei Province. The results show that clinopyroxenes were formed in all the reactions between the alkaline basaltic melt and orthopyroxenes under the studied P–T conditions. The formation of clinopyroxene in the reaction zone is mainly controlled by dissolution–crystallization, and the chemical compositions of the reacted melt are primarily influenced by the diffusion effect. Temperature is the most important parameter controlling the reactions between the melt and orthopyroxenes, which has a direct impact on the melting of orthopyroxenes and the diffusion of chemical components in the melt. Temperature also directly controls the chemical compositions of the newly formed clinopyroxenes in the reaction zone and the reacted melt. The formation of clinopyroxenes from the reactions between the alkaline basaltic melt and orthopyroxenes can result in an increase of CaO and Al₂O₃ contents in the rocks containing this mineral. Therefore, the reactions between the alkaline basaltic melt from the asthenospheric mantle and orthopyroxenes from the lithospheric mantle can lead to the evolution of lithospheric mantle in the North China Craton from refractory to fertile with relatively high CaO and Al₂O₃ contents. In addition, the reacted melts in some runs were transformed from the starting alkaline basaltic into tholeiitic after reactions, indicating that tholeiitic magma could be generated from alkaline basaltic one via reactions between the latter and orthopyroxene.

DOI: 10.1007/s11631-023-00671-1

Source: https://link.springer.com/article/10.1007/s11631-023-00671-1