In the southernmost Appalachians, bimodal volcanics of Pumpkinvine Creek Formation (PCF) and its proposed equivalent, the Hillabee Greenstone (HG) have indistinguishable ages (~460 Ma) and trace element-REE pattern similar to an arc/back-arc type setting. Eplison 143Nd values of felsic members of the HG and PCF indicate involvement of Grenville crust during petrogenesis. U-Pb dates (900-1500)Ma of detrital zircons in PCF meta-sandstone cluster around 1100Ma. Nd-model ages of the Ashland-Wedowee Supergroup metasediments range between 943-1439 Ma and cluster around 1000 Ma. Rb-Sr whole rock and U-Pb zircon dates of the Mulberry Rock Gneiss also demonstrate an Ordovician age (~460 Ma). It is concluded that the PCF-HG arc formed on the Laurentian continental margin on Ashland-Wedowee sediments during Ordovician and remained outboard of the continent until final closure during Alleghenian orogeny. Geochronological investigations of the Tres Piedras Granite of northcentral New Mexico have revealed a sharp discordancy between Rb-Sr whole-rock and U-Pb zircon ages. Analyses of fifty individual zircons (most concordant) by LA-MS-ICPMS yield a ~1730 Ma magmatic crystallization age. Rb-Sr whole-rock isochron ages from separate localities are 1490+/-20 Ma and 1497+/-42 Ma. Sphene/whole-rock/biotite isochron ages and initial 87Sr/86Sr ratios from separate localities are indistinguishable from those of whole-rock isochrons. In both cases feldspar plots above the isochrons and appeared to be an open system as evidenced by 4% difference in 87Sr/86Sr in the core and rim of feldspar. Taken altogether, these data are interpreted to reflect a large (kilometer) scale redistribution and rehomogenization of strontium isotopes during an independently, well-documented metamorphic event in the region. The geochemical character of the Kutch volcanics, northwest of Deccan Traps, India, have been investigated in order the magma's origin. Sr-Nd-Pb isotopic ratios and trace element patterns identifies three end members: Reunion plume-type alkali basalts, Mahabaleshwar-type alkali basalts and crustally contaminated tholeiites. The first type of alkali basalts that can be generated by very low degree of partial melting (1.6-1.8%) of Reunion plume like source at garnet stability field; the tholeiites can be explained by crustal contamination of Indian-MORB like magma. High 207Pb/204Pb (15.61-15.83) ratio of the tholeiites agrees well with the Pb-isotopes of local Archean crust. / A Dissertation submitted to the Department of Geological Sciences in partial
fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Fall Semester, 2006. / Date of Defense: November 1, 2006. / Pumpkinvine Creek Formation, Back Arc Lavas, Isotopic Homogenization, Hillabee Greenstone, Kutch Volcanics / Includes bibliographical references. / A. Leroy Odom, Professor Directing Dissertation; Jeffrey Chanton, Outside Committee Member; Stephen A. Kish, Committee Member; Vincent J. M. Salters, Committee Member; James F. Tull, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_169021 |
| Contributors | Das, Reshmi (authoraut), Odom, A. Leroy (professor directing dissertation), Chanton, Jeffrey (outside committee member), Kish, Stephen A. (committee member), Salters, Vincent J. M. (committee member), Tull, James F. (committee member), Department of Earth, Ocean and Atmospheric Sciences (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
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