Abstract
Various forms of feldspar intergrowth microtextures occurred in granitic rocks. Characteristically, two distinct types of microtextures formed due to intergrowth between K-feldspar and plagioclase i.e. perthites and myrmekites. Malanjkhand and Dongargarh granitoids are two contemporaneous units of Paleoproterozoic granitoids in central India. Three varieties of perthites have been identified in these granitoids i.e. flame, braid, and vein types. Flame perthite bearing K-feldspar is common. Braid and vein perthites occur occasionally. Paleopiezometry estimation indicates that flame perthite formed under the influence of low to moderate differential stress on granitoids. Most of the perthites occurs in these granitoids are compositionally albite to oligoclase in nature. The composition ranges XAb: 0.98–0.49 for the Malanjkhand and XAb: 0.96–0.49 for Dongargarh granitoids. Binary feldspar thermometry calculation indicates that perthites have formed at moderate to high temperature conditions in the Malanjkhand granitoid whereas low to moderate temperature conditions in Dongargarh granitoids during sub-solidus phase. Myrmekites is another feldspar intergrowth microtexture found in these granitoids. Myrmekites are identified in these granitoids based on their characteristic morphologies such as ghost, bulbous, rim, etc. These myrmekites were formed under moderate temperature conditions during magmatic-hydrothermal transition phase. Formation of flame perthite can be explained by replacement reaction mechanism (Na-K exchange) between K-feldspar and plagioclase under low to moderate differential stress condition during rapid cooling. Further, extensive deuteric alteration results in the formation of braid and vein perthites. Formation of myrmekites can be assumed by couple of replacement mechanisms (Na-K and Ca-K exchange) between K-feldspar and plagioclase. Paleopiezometry and feldspar thermometry results infer that orthomagmatic-hydrothermal transition in the Malanjkhand and Dongargarh granitoids were favored at upper or shallow levels in the continental crust.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.