skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Petrology and geochemistry of lower crustal granulites from the Geronimo Volcanic Field, southeastern Arizona

Abstract

Mafic to intermediate composition granulite xenoliths occur in Pliocene to Recent alkali basalts from the Geronimo Volcanic Field (GVF), southeastern Arizona, USA. The range of compositions and mineral assemblages observed suggests that the ultimate derivation of these rocks is from a variety of protoliths and that more than one mechanism has operated during the geologic evolution of the lower crust in this area. Two-pyroxene, two-feldspar granulites (meta-diorites) have major and trace element characteristics similar to estimates of post-Archaen lower crust. Low {sup 143}Nd/{sup 144}Nd values and Proterozoic Nd-depleted-mantle model ages (1.2-1.4 Ga) for these rocks require that Precambrian material exists in the lower crust of southeastern Arizona, either as the meta-diorites themselves or as older crust available for melting during production of the meta-diorite protoliths. K-feldspar-free granulites have more mafic compositions and their trace element characteristics are consistent with a cumulate origin. A negative correlation of {sup 208}Pb/{sup 204}Pb vs. {sup 206}Pb/{sup 204}Pb suggests that the meta-cumulate granulites represent mixing between Basin and Range age lavas with older meta-diorite crust and is, thus, evidence for Cenozoic underplating of the lower crust beneath the Basin and Range.

Authors:
;  [1];  [2];  [3]
  1. (The Open Univ., Milton Keynes (England))
  2. (NERC Isotope Geosciences Laboratory, Keyworth (England))
  3. (Department of Earth Sciences, Oxford (England))
Publication Date:
OSTI Identifier:
6053924
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geochimica et Cosmochimica Acta; (USA); Journal Volume: 54:12
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; ARIZONA; GRANULITES; GEOCHEMISTRY; PETROGENESIS; PETROLOGY; CHEMICAL COMPOSITION; ISOTOPE RATIO; MINERALOGY; VOLCANIC REGIONS; CHEMISTRY; FEDERAL REGION IX; GEOLOGY; METAMORPHIC ROCKS; NORTH AMERICA; ROCKS; USA; 580000* - Geosciences

Citation Formats

Kempton, P.D., Hawkesworth, C.J., Harmon, R.S., and Moorbath, S.. Petrology and geochemistry of lower crustal granulites from the Geronimo Volcanic Field, southeastern Arizona. United States: N. p., 1990. Web. doi:10.1016/0016-7037(90)90294-U.
Kempton, P.D., Hawkesworth, C.J., Harmon, R.S., & Moorbath, S.. Petrology and geochemistry of lower crustal granulites from the Geronimo Volcanic Field, southeastern Arizona. United States. doi:10.1016/0016-7037(90)90294-U.
Kempton, P.D., Hawkesworth, C.J., Harmon, R.S., and Moorbath, S.. 1990. "Petrology and geochemistry of lower crustal granulites from the Geronimo Volcanic Field, southeastern Arizona". United States. doi:10.1016/0016-7037(90)90294-U.
@article{osti_6053924,
title = {Petrology and geochemistry of lower crustal granulites from the Geronimo Volcanic Field, southeastern Arizona},
author = {Kempton, P.D. and Hawkesworth, C.J. and Harmon, R.S. and Moorbath, S.},
abstractNote = {Mafic to intermediate composition granulite xenoliths occur in Pliocene to Recent alkali basalts from the Geronimo Volcanic Field (GVF), southeastern Arizona, USA. The range of compositions and mineral assemblages observed suggests that the ultimate derivation of these rocks is from a variety of protoliths and that more than one mechanism has operated during the geologic evolution of the lower crust in this area. Two-pyroxene, two-feldspar granulites (meta-diorites) have major and trace element characteristics similar to estimates of post-Archaen lower crust. Low {sup 143}Nd/{sup 144}Nd values and Proterozoic Nd-depleted-mantle model ages (1.2-1.4 Ga) for these rocks require that Precambrian material exists in the lower crust of southeastern Arizona, either as the meta-diorites themselves or as older crust available for melting during production of the meta-diorite protoliths. K-feldspar-free granulites have more mafic compositions and their trace element characteristics are consistent with a cumulate origin. A negative correlation of {sup 208}Pb/{sup 204}Pb vs. {sup 206}Pb/{sup 204}Pb suggests that the meta-cumulate granulites represent mixing between Basin and Range age lavas with older meta-diorite crust and is, thus, evidence for Cenozoic underplating of the lower crust beneath the Basin and Range.},
doi = {10.1016/0016-7037(90)90294-U},
journal = {Geochimica et Cosmochimica Acta; (USA)},
number = ,
volume = 54:12,
place = {United States},
year = 1990,
month =
}
  • Boron contents are uniformly low in more than 100 granulites from exposed terranes in India, Norway, and Scotland, and from xenolith suites in the western US. Averages for the terranes (2.5 ppm) and for xenoliths (1.2 ppm) suggest maximum B contents of about 2 {plus minus} 1 ppm for the lower crust. Abundance distributions from exposed terranes are skewed to higher values as B has been added to some samples via retrograde fluids during decompression. The samples studied include mafic to felsic lithologies of both igneous and sedimentary origin. There is no correlation of B content with bulk composition ormore » with protolith type in any of the suites studied. Boron is apparently depleted in all granulite protoliths during prograde metamorphism and dehydration. Similar depletions of B and other fluid-mobile elements (e.g., U, Cs) with respect to rare-earth elements (REE) Zr, Ba, Rb, and K{sub 2}O are seemingly inconsistent with origin of granulites primarily via extraction of silicate melts. These distinctive geochemical features are attributed to selective element transport in fluids released by devolatilization reactions. Anatexis is not necessarily precluded, but dehydration of the subsolidus protolith normally would precede melting and lead to depletion of the fluid-mobile elements. Compositions of any melts and restites eventually formed would reflect the effects of this antecedent process. The systematic depletion of B (and Cs) in granulites contrasts with the highly variable contents of most other incompatible elements determined. For this reason, the estimated lower crust abundance for B is relatively well constrained, whereas abundance estimates for many other elements are model dependent, have large uncertainties and are unlikely to be globally representative.« less
  • A spatio-temporal near-neighbor model is used to identify and map variations in the recurrence rate of volcanism in the Springerville volcanic field, Arizona, a large field on the Colorado Plateau boundary. Detailed mapping of individual lava flows and their associated vents, together with radiometric and paleomagnetic dating, demonstrates that 366 volcanic events have formed the Springerville volcanic field. A near-neighbor spatio-temporal recurrence-rate model using seven near-neighbor volcanoes and a 0.5 m.y. time window reveals that (1) areas of waxing and waning magmatism in the Springerville volcanic field are much more localized and (2) volcanic activity within these areas is muchmore » more intense than implied by field-wide temporal trends. Because volcanic activity is spatially and temporally clustered, forecasting subsequent activity is more successful if the spatio-temporal recurrence-rate model is used, rather than the average recurrence rates. This success indicates that spatio-temporal recurrence-rate models are useful tools for the quantification of long-term volcanic hazards in basaltic volcanic fields. 61 refs., 13 figs., 2 tabs.« less
  • The Guffey volcanic center is the largest within the 2000 km{sup 2} mid-Tertiary Thirtynine Mile volcanic field of central Colorado. This study is the first to provide extensive chemical data for these alkalic volcanic and subvolcanic rocks, which present the eroded remnants of a large stratovolcano of Oligocene age. Formation of early domes and flows of latite and trachyte within the Guffey center was followed by extrusion of a thick series of basalt, trachybasalt, and shoshonite flows and lahars. Plugs, dikes, and vents ranging from basalt to rhyolite cut the thick mafic deposits, and felsic tuffs breccias chemically identical tomore » the small rhyolitic plutons are locally preserved. Whole-rack major and trace element analyses of 80 samples, ranging almost continuously from 47% to 78% SiO{sub 2}, indicate that the rocks of the Guffey center are among the most highly enriched in K{sub 2}O (up to 6%) and rare earth elements (typically 200-300 ppm) of any volcanic rocks in Colorado. These observations, along with the relatively high concentrations of Ba and Rb and the depletion of Cr and Ni, suggest an appreciable contribution of lower crustal material to the magmas that produced the Thirtynine Mile volcanic rocks.« less
  • An Eocene submarine boninite series volcanic center isexposed on the island of Chichi-jima, Bonin Islands, Japan. Five rocktypes, boninite, bronzite andesite, dacite, quartz dacite, and rhyolite,were distinguished within the boninite volcanic sequence on the basis ofpetrographic and geochemical observations. Boninite lavas contain highmagnesium, nickel, and chromium contentsindicative of primitive melts,but have high silica contents relative to other mantle-derived magmas.All boninite series lavas contain very low incompatible elementconcentrations, and concentrations of high-field strength elements inprimitive boninite lavas are less than half of those found in depletedmid-ocean ridge basalts. Abundances of large-ion lithophile elements arerelatively high in boninite series lavas, similar tomore » the enrichmentsobserved in many island arc lavas. Trends for both major and traceelement data suggest that the more evolved lavas of the boninite magmaseries were derived primarily through high-level fractionalcrystallization of boninite. Textural features, such as resorption andglomeroporphyrocrysts, and reverse chemical zonations suggest that magmamixing contributed to the development of the quartz dacitelavas.« less
  • Altered volcanic ashes (K-bentonites) in the late Ordovician (Caradocian) Utica shale of New York State are the product of explosive arc volcanism. Most of the 30 K-bentonites examined in this investigation contain fragmental crystals and rock fragments (microliths) up to 600 {mu}m in diameter that generally are neither detrital contamination from the surrounding black shale nor igneous phenocrysts. The dominant phases are garnet (two groups; Gr{sub 15-20}Alm{sub 45-75}Py{sub 35-0}Sp{sub 2-5}; Gr{sub 2-5}Alm{sub 55-85}Py{sub 10-40}Sp{sub 1}), plagioclase feldspar (An{sub 80-10}), alkali feldspar (Or{sub 99-0}), clinopyroxene (Wo{sub 50-40}En{sub 50-30}Fs{sub 0-30}), and orthopyroxene (Wo{sub 1-2}En{sub 77-32}Fs{sub 32-66}), accompanied by lesser quantities of hornblende,more » aluminosilicate, quartz, sphene, Fe-Ti oxides, apatite, and zircon. Most of the fragmental crystals appear to be derived from the same source as the metamorphic microliths, which possess minerals with similar compositions. Both crystals and microliths are interpreted as xenocrysts and xenoliths from the ancient continental crust on which the Ordovician arc was constructed. They became entrained in the volcanic plume during explosive eruptions. A Precambrian age acquired on K-feldspars from one K-bentonite using the {sup 40}Ar/{sub 39}Ar method shows that these xenocrysts were derived from depths of less than 5-10 km in the microcontinent at the time of late Ordovician volcanism. The occurrence of xenocrysts and xenoliths in these K-bentonites underscores the importance of performing detailed petrology on ash layers prior to the onset of more sophisticated tasks (e.g., isotopic age determinations; regional stratigraphic correlations of K-bentonites based upon chemical compositions).« less