Abstract

Staurolite stability in rocks of zonal metamorphic complexes and the subsequent decomposition of this mineral in the rocks at increasing temperature is a criterion for distinguishing the staurolite metamorphic zone. Along with other metamorphic zones, this zone reflects the temperature distribution configuration when the metamorphic zoning was formed. Staurolite-bearing mineral assemblages are formed in metapelites of appropriate chemical composition at metamorphic temperatures of ~500–650°C. The fact that staurolite is stable within a relatively narrow temperature range makes it possible to predict the presence or absence of this mineral in rocks if representative data on the composition of their protoliths are available. We propose a method for identifying potentially staurolite-bearing rocks using computational petrochemical modules, whose values are calibrated on natural rocks and modeled rock compositions that can occur in nature. Four petrochemical modules are proposed in the form of specified proportions of major chemical components in metamorphic rocks: Al₂O₃/SiO₂, CaO/FM (where FM = FeO_t + MgO), K₂O/FM, and Na₂O/FM. They can be used as criteria for estimating the possibility of staurolite crystallization in rocks when a suitable temperature (and pressure) is reached. These modules make it possible to select and more reliably specify the boundaries of the staurolite zone when, for example, maps of metamorphism are produced.

中文翻译：

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中温低中压变质变质岩中十字石稳定性的石化标准

摘要

带状变质复合体岩石中的十字石稳定性以及随后在岩石中随温度升高而分解的这种矿物是区分十字石变质带的标准。该带与其他变质带一样，反映了变质带形成时的温度分布构型。在约 500–650°C 的变质温度下，在具有适当化学成分的变质岩中形成含十字石的矿物组合。十字石在相对较窄的温度范围内是稳定的这一事实使得如果可以获得有关其原岩组成的代表性数据，则可以预测岩石中是否存在这种矿物。我们提出了一种使用计算石化模块识别潜在含有十字石的岩石的方法，其值根据天然岩石和自然界中可能发生的模拟岩石成分进行校准。以变​​质岩中主要化学成分的指定比例的形式提出了四个石化模块：Al₂ O ₃ /SiO ₂、CaO/FM（其中FM = FeO _t + MgO）、K ₂ O/FM 和Na ₂ O/FM。当达到合适的温度（和压力）时，它们可用作估计岩石中十字石结晶可能性的标准。例如，当制作变质图时，这些模块可以选择并更可靠地指定星石带的边界。