An inverse modeling approach to obtain P-T conditions of metamorphic stages involving garnet growth and resorption
An inverse modeling approach to obtain P-T conditions of metamorphic stages involving garnet growth and resorption
复制标题
获得涉及石榴石生长和吸收的变质阶段 P-T 条件的逆向建模方法
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
M. Engi
中科院分区：
文献类型：
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作者：
P. Lanari;F. Giuntoli;C. Loury;Marco Burn;M. Engi
本文提出了一种方法和一个计算机程序（GrtMod）的石榴石演化的数值模拟的基础上组成的连续生长区在天然样品。对于每个石榴石生长阶段，一个新的局部有效的整体组合物进行优化，允许再吸收和/或分馏先前结晶的石榴石。使用Nelder-Mead算法（一种启发式搜索方法）进行连续最小化。一个自动化的策略，包括两个优化阶段和一个细化阶段的描述和测试。该程序用于计算Sesia区（西阿尔卑斯山）石榴石中晶体生长的压力-温度（P-T）条件。连续生长区的组成变化的特点是使用标准化的X射线图和XMapTools程序。该模型表明，二叠纪石榴石核在T > 800 °C和P = 6 kbar的麻粒岩相条件下结晶。在阿尔卑斯山时期，第一个石榴石边缘在榴辉岩相条件下（650 °C，16 kbar）生长，以石榴石核心为代价。在较低的P（0.11kbar）和630 °C下添加第二边缘。总的来说，石榴石再吸收量为10.9%（体积）的阿尔卑斯山的演变过程中建模，这个值是支持我们的观察X射线成分图。
This contribution presents an approach and a computer program (GrtMod) for numerical simulation of garnet evolution based on compositions of successive growth zones in natural samples. For each garnet growth stage, a new local effective bulk composition is optimized, allowing for resorption and/or fractionation of previously crystallized garnet. The successive minimizations are performed using the Nelder–Mead algorithm; a heuristic search method. An automated strategy including two optimization stages and one refinement stage is described and tested. This program is used to calculate pressure–temperature ( P–T ) conditions of crystal growth as archived in garnet from the Sesia Zone (Western Alps). The compositional variability of successive growth zones is characterized using standardized X-ray maps and the program XMapTools. The model suggests that Permian garnet cores crystallized under granulite-facies conditions at T > 800 °C and P = 6 kbar. During Alpine times, a first garnet rim grew at eclogite-facies conditions (650 °C, 16 kbar) at the expense of the garnet core. A second rim was added at lower P (∼11 kbar) and 630 °C. In total, garnet resorption is modeled to amount to ∼9 vol% during the Alpine evolution; this value is supported by our observations in X-ray compositional maps.
影响因子：
3.9
作者：
Konrad-Schmolke, Matthias;O'Brien, Patrick J.;Zack, Thomas
通讯作者：
Zack, Thomas