The basement of eastern Mexico comprises Grenvillian-age granulite-facies metamorphic rocks. The Oaxacan Complex represents the largest outcrop belt of this basement in Mexico. In this work, southwestern Oaxacan Complex garnets are studied from a petrographical, geochemical, and geothermobarometrical perspective for the first time. The studied garnets display different grain sizes nucleated in a polyphase evolution. The almandine end member proportion is similar in all of the studied lithotypes. The highest pyrope concentrations are found in Qz Fsp paragenesis and ultramafic rocks and the lowest pyrope concentrations are found in amphibolite. The highest grossular and spessartine concentrations are found in the amphibolite lithotype. Southwestern Oaxacan Complex garnets from paraderivate samples are more enriched in Rb, Ba, Pb, Ni, and Zn than those from orthoderivate samples enriched in Ti and V. This fact is related to the nature of the protoliths and the mineral phases that fractionate the same minor and trace elements. Garnets from para- and orthoderivate samples display 0.02–1.1 Eu/Eu* anomalies. This fact indicates that almost all of the garnets formed while the plagioclase was stable, and it does not rule out the interpretation that some garnets were peritectic. The pressure obtained using a Grt-Opx-Pl-Qz geobarometer in the southwestern Oaxacan Complex is higher than the pressure obtained in the northern part of the Complex, and it is consistent with the pressure obtained in the Grenvillian-age granulites of the Novillo Gneiss from northeastern Mexico. Geothermobarometric studies reveal different P-T features at the study site, so different structural levels of the orogen are inferred.

中文翻译：

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来自西南瓦哈卡杂岩体（墨西哥南部）的 Grenvillian 粒状岩的高温变质石榴石：岩石学、地球化学、地热气压测量法和构造意义

墨西哥东部的基底包括 Grenvillian 时代麻粒岩相变质岩。Oaxacan Complex 是墨西哥该地下室最大的露头带。在这项工作中，首次从岩相学、地球化学和地温气压测量学角度研究了西南瓦哈坎杂岩石榴石。研究的石榴石显示出不同的晶粒尺寸，在多相演化中成核。在所有研究的岩型中，铁铝榴石端元比例相似。在 Qz Fsp 共生岩和超镁铁质岩中发现了最高的硅镁石浓度，在角闪岩中发现了最低的硅镁石浓度。在角闪石岩型中发现了最高的粗粒和锰铝榴石浓度。来自副衍生样品的西南瓦哈坎复合石榴石更富含 Rb、Ba、Pb、Ni、和 Zn 比来自富含 Ti 和 V 的正衍生样品的样品少。这一事实与原岩的性质和分馏相同微量元素和微量元素的矿物相有关。来自准和正衍生物样品的石榴石显示 0.02–1.1 Eu/Eu* 异常。这一事实表明，几乎所有的石榴石都是在斜长石稳定时形成的，不排除一些石榴石是包晶的解释。在瓦哈卡杂岩体西南部使用 Grt-Opx-Pl-Qz 地球气压计获得的压力高于在该杂岩体北部获得的压力，并且与在 Novillo 片麻岩的 Grenvillian 时代麻粒岩中获得的压力一致来自墨西哥东北部。地热气压研究揭示了研究地点的不同 PT 特征，