花岗岩浆形成定位机制的思考与研究进展

发布时间：2018-08-11 14:13

【摘要】：花岗岩(广义)是陆壳的标志,也是地球岩石圈区别于其它行星岩石圈的标志。文章介绍了行星探测和大洋调查等方面的成果对花岗岩形成的地质约束:行星从岩浆表壳向岩石表壳转换过程以及现代地幔过程,均没有产生有规模意义的花岗岩;花岗岩及其所标志的陆壳,应是星球出现水圈和沉积岩之后的产物;花岗岩在地球岩石圈二维空间上的平均生长速率,大约为485×10~3km~2/Myr;岩浆主要来自地壳岩石的部分熔融(深熔)。在此基础上,文章介绍了深熔作用方面的研究进展,讨论了部分熔融岩石的流变行为与其内熔体比的关系,并比较了岩浆侵入模型与岩浆对流模型在解释花岗岩形成定位机制方面的异同。侵入模型的困难之一来自岩体与源区分离。由于源区位于岩体下方且远离岩体,因而是不可观察的,除非岩体及其与源区之间的岩石因风化或构造被剥蚀殆尽。文章最后介绍了"深熔-对流"模型的研究进展。该模型认为"源区"与"定位区间"是统一的,当"源区"岩石的熔体比例超过流变学的临界熔体比,岩石转变为"脏"岩浆;"脏"岩浆层内的重力分异诱发热对流,后者引起"顶蚀作用",导致重熔界面(MI)或固-液转换界面(SLT)不断向上移动和岩浆层的逐渐增厚。基本认识是:熔区内的热对流是深熔作用能够形成大规模花岗岩浆的必要条件;没有对流,陆壳岩石的部分熔融只能产生混合岩,不能产生岩基规模的花岗岩。
[Abstract]:Granite (broad sense) is the symbol of continental crust and the difference between lithosphere and other planetary lithosphere. This paper introduces the geological constraints on the formation of granites from planetary exploration and oceanic survey: neither the transformation process of the planets from magmatic crust to rock surface crust nor the modern mantle process produced significant granites on a large scale; The granite and its marked continental crust should be the product of hydrosphere and sedimentary rocks, the average growth rate of granites in the two-dimensional space of the lithosphere is about 485 脳 10 ~ (3) km ~ (-1) ~ (2 /) Myr, and the magma mainly comes from the partial melting (deep melting) of the crustal rocks. On this basis, this paper introduces the research progress of deep melting, and discusses the relationship between the rheological behavior of partially melted rock and its melt ratio. The similarities and differences between magmatic intrusion model and magmatic convection model in explaining the localization mechanism of granite formation are also compared. One of the difficulties of the intrusive model is the separation of the rock mass from the source area. Because the source is below and far from the rock mass, it is not observable unless the rock mass and the rocks between it and the source area are completely eroded by weathering or tectonics. At the end of this paper, the research progress of the "deep melt-convection" model is introduced. The model holds that the "source region" and "location zone" are unified. When the melt ratio of the "source" rock exceeds the critical melt ratio of rheology, the rock becomes "dirty" magma, and the thermal convection is induced by gravity differentiation in the "dirty" magmatic layer. The latter causes "top erosion", which leads to the continuous upward movement of (MI) or (SLT) at the solid-liquid transition interface and the gradual thickening of the magmatic layer. The basic understanding is that the thermal convection in the melting zone is a necessary condition for the formation of large granitic magma by deep melting, and without convection, the partial melting of continental crust rocks can only produce mixed rocks, not granite of rock base size.
【作者单位】：中山大学地球科学与工程学院;广东省矿床资源与地质过程重点实验室;吉林大学地球科学学院;
【基金】：国家自然科学基金项目(41372223)资助
【分类号】：P588.121

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