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首页> 外文期刊>Brazilian Journal of Geology >Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Ara?uaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results
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Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Ara?uaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results

机译：以巴伊亚州南部Ara？uaí造山带的岩石为例，热压法在辉石和花岗石中的应用和局限性，包括对当前结果的构造意义的讨论

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In southern Bahia, there are outcrops of migmatites and granulites in the Jequitinhonha Complex, which is part of the northern portion of the Ara?uaí Orogen. Migmatites (garnet-cordierite diatexite) dominate the metamorphic rocks and host lenses and layers of felsic garnet granulite. The conditions of temperature and pressure of metamorphism were calculated using conventional thermobarometry and the software THERMOCALC. Values around 850 °C and 7 kbar were obtained with THERMOCALC. The calculations for the garnet-cordierite diatexite were made considering aH2O equal to 1, but the best results of calculations for the granulites are obtained with aH2O values of 0.3. Pressure values obtained with GAPES resulted in consistent values with THERMOCALC, but the pair garnet-orthopyroxene always produces low values for temperature and high ones for pressure. The results are consistent with the presence of the pair garnet and cordierite in diatexite and orthopyroxene in felsic granulite. From the tectonic point of view, the setting in which metamorphism of these rocks occurred requires high heat flow with a thermal anomaly in mid continental crust, as indicated by values of 7 kbar. Recent studies have favored the closure of a back-arc basin for this tectonic setting, but it does not solve the problem that the time span between metamorphic peak and the end of granite intrusions, involving large bodies of charnockite, is more than 80 million years. The model of tectonic switching is suggested here as it can explain the maintenance of high temperatures for a more extended interval of time.
机译：在巴伊亚州南部，位于Ara？uaí造山带北部的Jequitinhonha Complex中有大量的辉长岩和花岗石露头。玛格石（石榴石-堇青石的辉绿岩）主导着变质岩，主晶状体和长英质石榴石花岗石层。使用常规热压法和软件THERMOCALC计算了变质的温度和压力条件。用THERMOCALC获得的温度约为850°C和7 kbar。石榴石-堇青石渗碳体的计算是考虑aH2O等于1，但以0.3的aH2O值可获得最佳的花岗石计算结果。用GAPES获得的压力值与THERMOCALC的值一致，但是石榴石-邻二甲苯对总是产生较低的温度值，而产生较高的压力值。结果与在闪长岩中的石榴石和堇青石对在辉绿岩中和邻辉石中存在石榴石和堇青石相一致。从构造的观点来看，这些岩石发生变质的环境需要高热流，并且在中大陆壳中存在热异常，如7 kbar的值所示。最近的研究倾向于在这种构造背景下关闭后弧盆地，但是它并没有解决变质峰到花岗岩侵入（包括大块的菱镁矿）末端之间的时间跨度超过8000万年的问题。 。这里提出了构造转换模型，因为它可以解释在更长的时间间隔内维持高温的原因。

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