Intracrystalline exsolution textures in alkali feldspar are common in lithotypes from many alkaline complexes of the Eastern Ghats Granulite Belt (EGGB), India. However, the parentage of these textures and their compositional evolution is not well documented from this granulite belt. This study on the Koraput Alkaline Complex (KAC) in the EGGB documents the exsolution textures from several lithologies, establishes their igneous origin and finally links their compositional modifications with the evolutionary history of the complex. The studied exsolution textures belong to both perthite and mesoperthite. To estimate the temperature of formation of these textures, we used both two-feldspar thermometry, and one-feldspar thermometry following several models. In two-feldspar thermometry, compositions of exsolved alkali feldspar and the adjacent plagioclase feldspar pairs were used. In one-feldspar thermometry, the reintegrated compositions of exsolved alkali feldspars were used. The maximum temperature of formation of exsolution lamellae estimated from two-feldspar thermometry for mesoperthites in nepheline syenite is > 841 °C, and for perthites is > 759 °C, at 7 kbar pressure. Compositions of initially formed plagioclase feldspar lamellae and the host feldspar were more orthoclase rich and more albite rich respectively compared to the observed compositions. Using one-feldspar thermometry the calculated temperatures for alkali gabbro, syenite and alkali feldspar granite are > 870 °C, > 810 °C and > 730 °C, respectively. Compositions of alkali feldspars immediately before exsolution in these rocks were also estimated. Albite and orthoclase contents were nearly equal in mesoperthites; on the other hand, orthoclase content was higher than albite in perthites. Previous studies assigned their thermometric estimation with the minimum temperature of metamorphism that the KAC experienced, but the Ultra High Temperature (UHT) record obtained from the feldspar thermometry of the present study is difficult to correlate with these metamorphic events. Instead, these high temperatures may represent an igneous condition, which remained unaffected throughout the later metamorphic event as documented from nepheline syenite.

碱性长石的晶内外溶结构在印度东高止山脉花岗岩带 (EGGB) 的许多碱性杂岩的岩型中很常见。然而，这些纹理的起源及其成分演化并没有从这条麻粒岩带中得到很好的记录。这项关于 EGGB 中 Koraput 碱性杂岩 (KAC) 的研究记录了几种岩性的外溶结构，确定了它们的火成岩起源，并最终将它们的成分变化与杂岩的演化历史联系起来。所研究的外溶质结构属于perthite 和mesoperthite。为了估计这些纹理的形成温度，我们使用了双长石温度计和遵循几个模型的单长石温度计。在双长石测温中，使用了溶解的碱性长石和相邻的斜长石对的成分。在单长石测温中，使用了溶解的碱性长石的重新整合组合物。在 7 kbar 压力下，霞石正长岩中的中磷长石由双长石测温估计的外溶薄片形成的最高温度为 > 841 °C，而对于 perthite，则为 > 759 °C。与观察到的成分相比，最初形成的斜长石片晶和主体长石的成分分别更富含正长石和更富含钠长石。使用单长石测温法，碱金属辉长岩、正长岩和碱长石花岗岩的计算温度分别为 > 870 °C、> 810 °C 和 > 730 °C。还估计了这些岩石中即将溶解之前的碱性长石的成分。钠长石和正长石的含量在中长石中几乎相等；另一方面，钙长石中的正长石含量高于钠长石。以前的研究将他们的温度估计与 KAC 经历的最低变质温度联系起来，但从本研究的长石温度测量中获得的超高温 (UHT) 记录很难与这些变质事件相关联。相反，这些高温可能代表了一种火成状态，如霞石正长岩所记录的那样，在整个后期变质事件中都没有受到影响。以前的研究将他们的温度估计与 KAC 经历的最低变质温度联系起来，但从本研究的长石温度测量中获得的超高温 (UHT) 记录很难与这些变质事件相关联。相反，这些高温可能代表了一种火成状态，如霞石正长岩所记录的那样，在整个后期变质事件中都没有受到影响。以前的研究将他们的温度估计与 KAC 经历的最低变质温度联系起来，但从本研究的长石温度测量中获得的超高温 (UHT) 记录很难与这些变质事件相关联。相反，这些高温可能代表了一种火成状态，如霞石正长岩所记录的那样，在整个后期变质事件中都没有受到影响。