GSA Connects 2021 in Portland, Oregon

Paper No. 53-3
Presentation Time: 2:30 PM-6:30 PM


MYERS, Joshua1, MENOLD, Carrie1 and MACRIS, Catherine A.2, (1)Earth & Environment, Albion College, Albion, MI 49224, (2)Department of Earth Sciences, Indiana University – Purdue University Indianapolis, 723 W Michigan Street, SL118, Indianapolis, IN 46202

Ultra-High Pressure (UHP) terranes record metamorphic histories in subduction and collisional settings. Early subducted pieces can preserve fluid-mobile elements derived from subduction and exhumation. This study focused on the eclogites found in the Himalayas in northwestern, India after subduction during exhumation. The Tso Morari complex is a quartzo-feldpathic gneiss dome containing small, sparse eclogite blocks. The eclogite used for this project is ~15 x 8 meter boudinaged block. Samples were collected along a row from the core to the outer rim of the eclogite to the center. The eclogite block preserves eclogite facies minerals in the core and has been altered to amphibolite facies at the rim. Minerals such as omphacite, rutile, garnet, and phengite are present in the eclogite facies core of the block. Moreover, the amphibolite facie indicate amphibole, hornblende, biotite, muscovite, quartz and hematite are present in the rim of the block. In addition to the petrology and textural analysis, all the eclogite samples were analyzed for whole rock geochemistry. Both major and trace elements were collected. By studying the chemistry and mineralogy of the core vs. rim samples we hope to understand the significance of the chemical exchange of elements with the gneiss during the exhumation, and better understand the regional metasomatism during exhumation from UHP conditions. Major and trace element graphs were produced to identify geochemical trends in the eclogite samples. The data was used to chemically illustrate the similarities and differences of each sample along the traverse. Eclogites furthest from the contact with the gneiss are part of the core of the block and preserve eclogite facies, while the rim samples close to the contact are amphibolitized. The high proportion of hydrous minerals indicate the presence of abundant fluid as the rocks were emplaced in the crust. The rim samples are enriched in K depleted in Mg relative to the core; they are also enriched in mobile trace elements Ba and Rb. Enrichment in the rim of the eclogite block suggests the metamorphic fluids brought mobile elements and deposited them in the chemical reactive contact region during the growth of amphibole and white mica.