Garnet-biotite thermometry, garnet-aluminum silicate-silica-plagioclase barometry, and Emp monazite geochronology of the early Proterozoic Ivanpah Mountains, eastern Mojave Desert, Se California
type: CreativeWork
description: Metamorphic fabric measurements indicate only one deformational fabric (NNE) is present in the Ivanpah Mountains, indicating that the area experienced one orogenic event during the Early Proterozoic. Peak P-T conditions, using garnet-Al2SiO5-silica-plagioclase barometry and garnet-biotite thermometry, were ∼4.0kb and >700Ã‚Â°C, respectively. Peak metamorphic-T's were recorded by the largest garnet studied; Electron Microprobe Analysis on monazite, using U-Th-Pb radioactive decay, suggest metamorphism occurred between 1752 +/- 86 Ma and 1689 +/- 34 Ma, similar to the age of the Yavapai terrane (∼1.70--1.69 Ma). These ages are constrained from six monazite grains included in three large garnets (2250--5000um). Matrix monazite from granitic rocks indicate magmatism may have occurred between 1559 +/- 31 Ma and 1416 +/- 28 Ma. Large garnets effectively shield monazite from Pb-loss when temperature is exceeded above what is considered its closure-T for radiogenic-Pb (∼700Ã‚Â°C), thus petrographic location is also a function of closure-T of radiogenic-Pb in monazite.
abstract: Metamorphic fabric measurements indicate only one deformational fabric (NNE) is present in the Ivanpah Mountains, indicating that the area experienced one orogenic event during the Early Proterozoic. Peak P-T conditions, using garnet-Al2SiO5-silica-plagioclase barometry and garnet-biotite thermometry, were ∼4.0kb and >700Ã‚Â°C, respectively. Peak metamorphic-T's were recorded by the largest garnet studied; Electron Microprobe Analysis on monazite, using U-Th-Pb radioactive decay, suggest metamorphism occurred between 1752 +/- 86 Ma and 1689 +/- 34 Ma, similar to the age of the Yavapai terrane (∼1.70--1.69 Ma). These ages are constrained from six monazite grains included in three large garnets (2250--5000um). Matrix monazite from granitic rocks indicate magmatism may have occurred between 1559 +/- 31 Ma and 1416 +/- 28 Ma. Large garnets effectively shield monazite from Pb-loss when temperature is exceeded above what is considered its closure-T for radiogenic-Pb (∼700Ã‚Â°C), thus petrographic location is also a function of closure-T of radiogenic-Pb in monazite.
author: Shields, David Allen
language: English
date published: 2003-01-01T08:00:00Z
date modified: 2026-07-24T05:25:40Z
provider: University of Nevada - Las Vegas
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Nevada, Las Vegas

PropertyValue
property ID: DOI
value: 10.25669/nrt1-1gf3