The University of Southampton
University of Southampton Institutional Repository

A strontium isotope evolution model for cenozoic magma genesis, Estern Great Basin, U.S.A.

A strontium isotope evolution model for cenozoic magma genesis, Estern Great Basin, U.S.A.
A strontium isotope evolution model for cenozoic magma genesis, Estern Great Basin, U.S.A.


Cenozoic volcanism in the Great Basin is characterized by an outward migration of volcanic centers with time from a centrally located core region, a gradational decrease in the initial Sr87/Sr86 ratio with decreasing age and increasing distance from the core, and a progressive change from calc-alkalic core rocks to more alkalic basin margin rocks. Generally each volcanic center erupted copious silicic ignimbrites followed by small amounts of basalt and andesite. The Sr82/Sr86 ratio for old core rocks is about 0.709 and the ratio for young basin margin rocks is about 0.705. Spatially and temporally related silicic and mafic suites have essentially the same Sr87/Sr86 ratios.

The locus of older volcanism of the core region was the intersection of a north-south trending axis of crustal extension and high heat flow with the northeast trending relic thermal ridge of the Mesozoic metamorphic hinterland of the Sevier Orogenic Belt. Derivation of the Great Basin magmas directly from mantle with modification by crustal contamination seems unlikely. Initial melting of lower crustal rocks probably occurred as a response to decrease in confining pressure related to crustal extension. Volcanism was probably also a consequence of the regional increase in the geothermal gradient that is now responsible for the high heat flow of the Basin and Range Province.

High Sr isotopic ratios of the older core volcanic rocks suggests that conditions suitable for the production of silicic magmas by partial fusion of the crust reached higher levels within the crust during initial volcanism than during production of later magmas with lower isotopic ratios and more alkaline chemistry. As the Great Basin became increasingly attenuated, progressively lower portions of the crust along basin margins were exposed to conditions suitable for magma genesis. The core region became exhausted in low temperature melting components, and volcanism ceased in the core before nearby areas had completed the silicic-mafic eruption cycle leading to their own exhaustion of crustal magma sources.
0258-8900
1-26
Scott, R.B.
9c3cf264-1784-4f5b-a70d-efbe923ddcfc
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Dasch, E. Julius
5aca8928-9f80-442e-a3b4-bbad9129d753
Armstrong, R.L.
8257102d-cf4f-4bc4-91e1-09428231154f
Scott, R.B.
9c3cf264-1784-4f5b-a70d-efbe923ddcfc
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Dasch, E. Julius
5aca8928-9f80-442e-a3b4-bbad9129d753
Armstrong, R.L.
8257102d-cf4f-4bc4-91e1-09428231154f

Scott, R.B., Nesbitt, R.W., Dasch, E. Julius and Armstrong, R.L. (1971) A strontium isotope evolution model for cenozoic magma genesis, Estern Great Basin, U.S.A. Bulletin of Volcanology, 35 (1), 1-26. (doi:10.1007/BF02596806).

Record type: Article

Abstract



Cenozoic volcanism in the Great Basin is characterized by an outward migration of volcanic centers with time from a centrally located core region, a gradational decrease in the initial Sr87/Sr86 ratio with decreasing age and increasing distance from the core, and a progressive change from calc-alkalic core rocks to more alkalic basin margin rocks. Generally each volcanic center erupted copious silicic ignimbrites followed by small amounts of basalt and andesite. The Sr82/Sr86 ratio for old core rocks is about 0.709 and the ratio for young basin margin rocks is about 0.705. Spatially and temporally related silicic and mafic suites have essentially the same Sr87/Sr86 ratios.

The locus of older volcanism of the core region was the intersection of a north-south trending axis of crustal extension and high heat flow with the northeast trending relic thermal ridge of the Mesozoic metamorphic hinterland of the Sevier Orogenic Belt. Derivation of the Great Basin magmas directly from mantle with modification by crustal contamination seems unlikely. Initial melting of lower crustal rocks probably occurred as a response to decrease in confining pressure related to crustal extension. Volcanism was probably also a consequence of the regional increase in the geothermal gradient that is now responsible for the high heat flow of the Basin and Range Province.

High Sr isotopic ratios of the older core volcanic rocks suggests that conditions suitable for the production of silicic magmas by partial fusion of the crust reached higher levels within the crust during initial volcanism than during production of later magmas with lower isotopic ratios and more alkaline chemistry. As the Great Basin became increasingly attenuated, progressively lower portions of the crust along basin margins were exposed to conditions suitable for magma genesis. The core region became exhausted in low temperature melting components, and volcanism ceased in the core before nearby areas had completed the silicic-mafic eruption cycle leading to their own exhaustion of crustal magma sources.

Full text not available from this repository.

More information

Published date: 1971
Organisations: Geochemistry

Identifiers

Local EPrints ID: 361871
URI: https://eprints.soton.ac.uk/id/eprint/361871
ISSN: 0258-8900
PURE UUID: fca7cceb-1c6c-4265-b414-eb718c35a40e

Catalogue record

Date deposited: 04 Feb 2014 16:58
Last modified: 18 Jul 2017 02:57

Export record

Altmetrics

Contributors

Author: R.B. Scott
Author: R.W. Nesbitt
Author: E. Julius Dasch
Author: R.L. Armstrong

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×