Rapid uplift and crustal growth in extensional environments: An isotopic study from the Death Valley region, California

Research Article| March 01, 1990 Rapid uplift and crustal growth in extensional environments: An isotopic study from the Death Valley region, California Yemane Asmerom; Yemane Asmerom 1Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massaschusetts 02138 Search for other works by this author on: GSW Google Scholar J. Kent Snow; J. Kent Snow 1Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massaschusetts 02138 Search for other works by this author on: GSW Google Scholar Daniel K. Holm; Daniel K. Holm 1Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massaschusetts 02138 Search for other works by this author on: GSW Google Scholar Stein B. Jacobsen; Stein B. Jacobsen 1Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massaschusetts 02138 Search for other works by this author on: GSW Google Scholar Brian P. Wernicke; Brian P. Wernicke 1Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massaschusetts 02138 Search for other works by this author on: GSW Google Scholar Daniel R. Lux Daniel R. Lux 2Department of Geological Sciences, University of Maine, Orono, Maine 04469 Search for other works by this author on: GSW Google Scholar Geology (1990) 18 (3): 223–226. https://doi.org/10.1130/0091-7613(1990)018<0223:RUACGI>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Yemane Asmerom, J. Kent Snow, Daniel K. Holm, Stein B. Jacobsen, Brian P. Wernicke, Daniel R. Lux; Rapid uplift and crustal growth in extensional environments: An isotopic study from the Death Valley region, California. Geology 1990;; 18 (3): 223–226. doi: https://doi.org/10.1130/0091-7613(1990)018<0223:RUACGI>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Willow Spring Diorite, in the Black Mountains of the central Death Valley extended terrain, yields a U-Pb zirocn age of 11.6 ±0.2 Ma. 40Ar-39Ar analyses of hornblende and U-Pb analyses of sphene from this sample give ages of about 10 Ma, indicating that the batholith remained above about 500 °C for about 1.5m.y. after crystallization. Geologic relations indicate that the diorite was exposed to erosion by about 5 Ma, bracketing the evolution of the diorite within the time between onset of extension and uplift of the Black Mountain crustal block. Initial 87Sr/86Sr ratios range from 0.7060 (mafic diorite) to 0.7083 (felsic diorite) in samples collected from an area 200 x 100 m. These data, combined with structural and petrologic evidence, suggest that the batholith represents a rare view of a mid-crustal zone of mixing between mantle-derived magma and crustal material, often suggested to exist on the basis of observations of intermediate volcanic rocks. The Black Mountains may therefore expose a cross section through a continental rift magmatic system, from partially contaminated mafic to intermediate intrusive rocks in the deep crust up to their volcanic equivalents. The relatively low initial 87Sr/86Sr and high ϵNd(-1.4) of the diorite, which is within Proterozoic basement with ϵNd ∼-18, is consistent with significant amounts mantle input in continental rifts inferred from geophysical data and measurement of He isotopic ratios. Such additions to the crust in continental rifts may represent a significant process crustal growth. Futhermore, the emplacement of igneous bodies with a large mantle component may help reconcile the large crustal pull apart in the Basin and Range (in excess of 140 km) with the fact that the crust still has no normal thickness of about 30-35 km. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.