Nature of basalt-deep crust interaction in the petrogenesis of a potassium-rich, silicic-dominated eruptive system, Davis Mountain volcanic field, west Texas
- Northern Illinois Univ., Dekalb, IL (United States). Dept. of Geology
The Davis Mountain volcanic field (DMVF) is one of several silicic-dominated eruptive centers that constitute the bulk of the Trans Pecos volcanic province (TPVP). New major-, trace element, and Pb-O isotope data on local granulite-facies xenoliths and the DMVF are used in evaluating the extent of basalt-deep crust interaction to produce voluminous silicic lavas and -ignimbrites. The DMVF (39.3--35.4 Ma) is a high-K, alkali basalt-potassic trachybasalt-shoshonite-latite-trachyte-rhyolite volcanoplutonic series with the evolved members being silica-saturated. DMF silicic rocks are characterized by high concentrations of Rb, Th, U, and K, low-[sup 18]O and have a broad range in Pb isotopes. These characteristics are inconsistent with an origin by partial melting of a Rb-Th-U depleted, unradiogenic Pb granulitic deep crust. However, distinctly different Pb isotope compositions between mafic and silicic rocks preclude an origin by fractional crystallization alone. Multistage-AFC involving a mantle-source, various proportions of OL-CPX-PLAG-KSPAR-MAG-AP-BIO-QTZ-aenigmatite-ZR differentiation, limited (<10%) amounts of deep and upper crustal contamination, and mixing between mafic and silicic magmas can satisfactorily account for the observed chemical and isotopic variation in the DMVF.
- OSTI ID:
- 5100009
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Geochemistry of high-potassium rocks from the mid-Tertiary Guffey volcanic center, Thirtynine Mile volcanic field, central Colorado
Contrasting styles of Pre-Cenozoic and mid-Tertiary crustal evolution in northern Mexico: Evidence from deep crustal xenoliths from La Olivina