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Origin of Lherzolite Inclusions in the Malapai Hill Basalt, Joshua Tree National Monument, California

1973; Geological Society of America; Volume: 84; Issue: 7 Linguagem: Inglês

10.1130/0016-7606(1973)84 2.0.co;2

1943-2674

Robert J. Stull, Kent McMillan,

Mineralogy and Gemology Studies

Research Article| July 01, 1973 Origin of Lherzolite Inclusions in the Malapai Hill Basalt, Joshua Tree National Monument, California ROBERT J. STULL; ROBERT J. STULL 1Department of Geology, California State University, Los Angeles, Los Angeles, California 90032 Search for other works by this author on: GSW Google Scholar KENT McMILLAN KENT McMILLAN 2Department of Geological Sciences, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar Author and Article Information ROBERT J. STULL 1Department of Geology, California State University, Los Angeles, Los Angeles, California 90032 KENT McMILLAN 2Department of Geological Sciences, Stanford University, Stanford, California 94305 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1973) 84 (7): 2343–2350. https://doi.org/10.1130/0016-7606(1973)84 2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation ROBERT J. STULL, KENT McMILLAN; Origin of Lherzolite Inclusions in the Malapai Hill Basalt, Joshua Tree National Monument, California. GSA Bulletin 1973;; 84 (7): 2343–2350. doi: https://doi.org/10.1130/0016-7606(1973)84 2.0.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 SocietyGSA Bulletin Search Advanced Search Abstract Alkali olivine basalt at Malapai Hill, California, occurs as a late Cenozoic stock that has intruded the Cretaceous White Tank Monzonite. The basalt is chemically and mineralogically similar to other alkaline basalts in the Mojave Desert, although it is devoid of zeolites. The strontium isotopic composition of the basalt (Sr87/Sr86 = 0.7030 ± 0.0006) suggests that it is derived from a mantle that has already experienced one period of partial melting. Olivine-rich Iherzolite nodules in the basalt are high in Mg and low in Si, Al, Ca, Na, and K. The nodules are xenomorphic granular with a tectonite fabric and forsteritic olivine (Fo94–88). The Sr87/Sr86 ratio of the nodules is 0.7043 ± 0.0008. Olivine xenocrysts and corroded xenolith margins suggest that reaction between the nodules and basalt has occurred.Similar Sr87/Sr86 ratios of Iherzolite nodules and alkali olivine basalt hosts at Malapai Hill are consistent with a related origin for the two rocks. The tectonite fabric and olivine composition of the nodules rule out a cognate origin by fractional crystallization of the basalt. Instead, the nodules are mantle materials that have been depleted in the most easily fusible elements by one or more periods of partial melting. The nodules may represent refractory residue from the area of partial melting or depleted mantle material, unrelated to the basalt but accidentally incorporated into it. Interpretation of the nodules as refractory residue from the site of melting is favored due to the similarity of the nodules and host rocks in strontium isotopic composition, the extreme chemical and petrologic uniformity of the inclusions, and chemical evidence that the nodules could be the end product of more than one partial melting. 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.