Abstract

The paper reports newly obtained data that append older results of experimental modeling of granitization processes. The experiments were aimed at modeling high-temperature metasomatism of mafic rocks, a process that involves the transfer of major components at 750°C and 500 MPa at a pressure gradient. The source of the transported Si, Ca, and Mg in the experiments was garnet. The solution was pure H₂O and 25 wt % NaCl aqueous solution. In the experiments, garnet was decomposed into pyroxenes, amphiboles, plagioclase, and minor amounts of melt, ilmenite, and iron oxides. The associated partial dissolution led to the transfer and redeposition of the dissolved components on the surface of a gabbroanorthosite underlay and to the development of mineral rims, which were analogous to those produced at garnet decomposition. The compositions of the newly formed minerals in the rims were identical to those produced at metamorphism of gabbroanorthosite at Т ≥ 750°C, P > 700 MPa. When the mineral rim was formed, some elements are removed, and this process was controlled by the composition of the fluid phase. The pure H₂O fluid removed Fe, Ca, and Mg. The aqueous fluid containing NaCl (X_NaCl ≈ 0.1) did not extract Ca from minerals. This indicates that no high NaCl concentrations are typical of fluid in processes that form basificates at granitization. The experiments have shown that H₂O and H₂O–NaCl fluids remove more Fe that other elements. Preferable Fe extraction from naturally occurring associations is evident from the elevated Fe mole fractions of the mafic minerals and from the fact that the basificates typically contain magnetite and hematite.

中文翻译：

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镁铁质岩石的粒化与高温交代作用：实验数据与自然观测结果的比较

摘要

该论文报告了新获得的数据，这些数据附加了粒化过程实验模型的较旧结果。实验的目的是模拟镁铁质岩石的高温交代作用，该过程涉及在750°C和500 MPa的压力梯度下转移主要成分的过程。实验中运输的硅，钙和镁的来源是石榴石。溶液是纯H ₂O和25重量％的NaCl水溶液。在实验中，石榴石被分解成辉石，闪石，斜长石和少量的熔体，钛铁矿和氧化铁。相关的部分溶解导致溶解的成分在辉长岩正石衬层表面上的转移和再沉积，并导致了矿物边缘的形成，类似于石榴石分解产生的矿物边缘。在轮缘新形成的矿物的组合物的那些相同。在gabbroanorthosite的变质产生在查阅商品说明Т ≥750℃，P > 700兆帕。当形成矿物边缘时，去除了一些元素，并且该过程由液相的组成控制。纯H ₂O流体去除了Fe，Ca和Mg。含NaCl（含水流体X_的NaCl ≈0.1）没有从矿物中提取的Ca。这表明在成粒过程中形成碱化物的过程中，流体中没有典型的高NaCl浓度。实验表明，与其他元素相比，H ₂ O和H ₂ O–NaCl流体能去除更多的铁。从镁铁矿矿物中铁摩尔分数的升高以及碱化金属通常含有磁铁矿和赤铁矿这一事实，可以清楚地证明从自然存在的缔合体中提取铁是优选的。