The petrology, geochemistry and origin of ultramafic inclusions and mafic alkaline volcanics from Ha...

مرکز و کتابخانه مطالعات اسلامی به زبان های اروپایی

منو

" The petrology, geochemistry and origin of ultramafic inclusions and mafic alkaline volcanics from Harrat Hutaymah, Saudi Arabia "
C. R. Thornber C. R. Stern

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1112482
Doc. No	:	TLpq303981257
Main Entry	:	C. R. Stern
	:	C. R. Thornber
Title & Author	:	The petrology, geochemistry and origin of ultramafic inclusions and mafic alkaline volcanics from Harrat Hutaymah, Saudi Arabia\ C. R. ThornberC. R. Stern
College	:	University of Colorado at Boulder
Date	:	1992
student score	:	1992
Degree	:	Ph.D.
Page No	:	271
Abstract	:	The purpose of this study is to evaluate geologic processes that are active in the subcrustal lithosphere during the rifting of a stable continental platform. This dissertation focuses on the petrologic, geochemical and isotopic systematics of continental-rift-related magmas and entrained xenoliths of mantle and deep crustal rocks. Harrat Hutaymah is an isolated, diatreme-dominated and xenolith-rich Tertiary/Quaternary volcanic field made up of basaltic magmas erupted through the continental lithosphere on the east flank of the Red Sea rift. P-T-X and time constraints on the of origin xenoliths, megacrysts and host magmas are established by combining petrographic and mineral chemical observations with available experimental phase-equilibria and thermobarometry, along with trace-element and Nd and Sr isotopic compositions. Igneous pyroxenites and melt-bearing peridotites of relatively high temperature affinity document processes that are cogenetic with Red Sea rift-related magmas erupted at Harrat Hutaymah over Late Tertiary to Quaternary time. Relative low-temperature, texturally-equilibrated metamorphic pyroxenites and non-melted peridotites provide a "frozen" record of a similar but older magmatic episode within the Arabian lithospheric mantle of Proterozoic age. Correlation of geochemical and isotopic characteristics in both syn-rift mantle-magma samples and pre-rift upper mantle rocks suggest that Hutaymah magmatism resulted from predominantly lithospheric as opposed to asthenospheric mantle melting. Major and trace element variations of Hutaymah magmas are shown to be controlled by the compositions of surrounding spinel lherzolite mantle and by fractional crystallization at subcrustal depths. Trace element modeling of partial-melts generated from Hutaymah spinel lherzolite compositions demonstrate the feasibility of generating primary rift-magmas at relatively shallow depths within the region of spinel-lherzolite stability (40 to 70 km).
Subject	:	Earth sciences
	:	Geology
	:	Geology
	:	magmas
	:	Mineralogy
	:	volcanics