Lower crustal evolution under central Arizona: Sr, Nd and Pb isotopic and geochemical evidence from the mafic xenoliths of Camp Creek

Esperança, Sonia; Carlson, Richard W.; Shirey, Steven B.

doi:10.1016/0012-821x(88)90108-2

Cited by 71 publications

(33 citation statements)

References 43 publications

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“…As suggested by xenoliths, the lower crust in central and southeastern Arizona is made up of granulite, amphibolite, and garnet-clinopyroxenite rock types (Esperança et al, 1988;Kempton et al, 1990). As suggested by xenoliths, the lower crust in central and southeastern Arizona is made up of granulite, amphibolite, and garnet-clinopyroxenite rock types (Esperança et al, 1988;Kempton et al, 1990).…”

Section: Cottonwood Spring Basaltsmentioning

confidence: 93%

Miocene basaltic magmatism in the Goldfield-Superstition volcanic province, central Arizona: Geochemistry, mineralogy, and petrology

Fodor

Vetter

2011

Rocky Mountain Geology

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Basaltic lavas form part of the Miocene (~20.5 to 18 Ma) Goldfield-Superstition silicic large igneous province in central Arizona. Most of the basalt erupted early in the development of this southern Basin and Range volcanic province, and only small amounts of basalt co-erupted with the silicic volcanism. We examined 50 samples of basalt from lower, middle, and upper stratigraphic positions of the province to establish basalt petrogeneses, the characteristics of basalt sources, relationships among compositionally different lavas, and the igneous processes that relate various basalt types. We base our study largely on major and trace elements, mineral compositions, and a small data set for Sr, Nd, and Hf isotopes.Lower-section basalts include the Weekes Wash basalts, which are transitional between alkalic and tholeiitic (SiO 2 49-51 wt. %) and with MgO 8.1-10.2 wt. %. They are associated with lavas that are andesitic (SiO 2 ~59-62 wt. %; MgO 8-2.5 wt. %) or are seemingly andesitic due to alteration and felsic xenocrysts. Weekes Wash basalts have incompatible-element abundances that correlate positively with MgO. Their 87 Sr/ 86 Sr ratios are ~0.705. Olivines, rarely fresh, have Fo 86-89 cores, and clinopyroxenes have Mg#s 86-89. Overlying the Weekes Wash are the Cottonwood Spring basalts, which are alkalic (SiO 2 ~45.5-47.5 wt. %), and can be categorized into subgroups defined by lower and higher incompatible-element abundances, or low Ti-P and high Ti-P (e.g., Ba ~1100 versus 1800 ppm; La ~75 versus 110 ppm). The Cottonwood Spring basalts are the closest to primary lavas we observed (MgO 10.1-11.8 wt. %), and their 87 Sr/ 86 Sr ratios are ~0.705-0.706. Their olivines are Fo 86-89 , and their clinopyroxenes have Mg#s 86-90. Overlying the Cottonwood Spring basalts is the Apache Gap Fe-Ti-enriched basalt (TiO 2 ~2.6 wt. %), which has the lowest MgO (~5.6-7.5 wt. %) and incompatible-element abundances observed for any basalts in the province (e.g., Ba ~400 ppm; La ~25 ppm). All lower-section basalts have primitive-mantle normalizations showing Nb-Ta negative anomalies.Middle-section basalts erupted among silicic lava and pyroclastic flows from ~19 to 18.5 Ma, and they compositionally resemble Weekes Wash basalts. Upper-section (post-18.5 Ma) lavas are the Willow Springs hawaiite (~9.5 wt. % MgO; 87 Sr/ 86 Sr ~0.705) and Black Mesa basanite (SiO 2 ~44 wt. %; MgO ~8 wt. %; CaO 14.7 wt. %; 87 Sr/ 86 Sr ~0.706). A Nb-Ta anomaly is clear in the hawaiite but weak in the basanite, as the basanite has the highest Nb and Ta observed (~60 and ~3 ppm; lowest Zr/Nb, ~4 versus all others >7).Relevant interpretations are the following. Absence of ultramafic mantle xenoliths in Goldfield-Superstition basalts suggests that magmas occupied crustal reservoirs. The two subgroups of the Cottonwood Spring basalts attest to small-scale trace element and isotopic heterogeneities in lithospheric mantle sources that, based on Nb-Ta and Ce versus Ce/Yb modeling, had subduction zone characteristics and were garnet bearing. For Weekes Wash basa...

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Section: Cottonwood Spring Basaltsmentioning

confidence: 93%

Miocene basaltic magmatism in the Goldfield-Superstition volcanic province, central Arizona: Geochemistry, mineralogy, and petrology

Fodor

Vetter

2011

Rocky Mountain Geology

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“…Detailed geochemical studies of such material to date have been confined to xenoliths brought to the surface via Tertiary magmas (Esperanca et al, 1988;Ruiz et al, 1988). In these cases, however, it cannot be determined unambiguously whether the xenoliths represent rock types that could have been the sources of Phanerozoic magmatism, or whether they represent material actually produced by Phanerozoic magma injection into the lower crust (Cameron and Robinson, 1990;Johnson, 1990).…”

Section: Summary and Future Workmentioning

confidence: 99%

Lower crustal and upper mantle xenoliths along the Cheyenne belt and vicinity

Lester

Farmer

1998

Rocky Mountain Geology

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Lower-crustal and upper-mantle xenoliths entrained in Phanerozoic igneous rocks in the northern Southern Rocky Mountains provide the only direct means of studying the petrologic and geochemical nature of the deep-continental lithosphere in this region. Petrographic and geochemical features of peridotite xenoliths from the State Line kimberlite district, near the Cheyenne belt, suggest that during Devonian kimberlite emplacement, infertile, cryptically metasomatized, Archean mantle dipped south beneath a distinctly more fertile, and veined, lithospheric mantle associated with the Proterozoic continental crust of the Colorado province. Lower-crustal xenoliths recovered from the State Line kimberlites and late Cenozoic ultrapotassic igneous rocks at Leucite Hills (north of the Cheyenne belt) are dominated by mafic granulites. This indicates that both the Archean and Proterozoic lower-continental crust was, and may remain today, mafic in composition.Existing major-element data support a tholeiitic basalt precursor for the mafic granulites associated with the Colorado province. Unfortunately, despite its importance for constraining models of lithospheric structure in the northern Rocky Mountains, detailed information regarding the age, trace element and isotopic compositions, or physical attributes of the mafic xenoliths is presently not available. In order to evaluate the age and composition of continental lithosphere in this region and to assess the possible role of mafic lower-crustal rock types as sources for Laramide magmatism we outline a plan (as part of the Rocky Mountain Continental Dynamics project) to obtain geochemical and geochronological information from xenoliths recovered at the State Line kimberlite district and Leucite Hills.

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“…It is reasonable to ask, therefore, whether Colorado Plateau basalts contain contributions from convecting upper mantle asthenosphere, and dissociated and rheologically transformed lithosphere entrained within it. The presence of pyroxenites, eclogites, and metasomatized peridotite in xenolith suites from the Colorado Plateau [ Esperanca et al ., ; McGuire and Mukasa , ; Smith et al ., ; Usui et al ., ; Porreca et al ., ; Usui et al ., ] suggests that sources for the Colorado Plateau basalts may have been more fertile than peridotite and more easily remobilized by thermal reactivation of the lithosphere. In support of this, paired Hf and Nd isotope characteristics of relatively evolved SF basalts define a strikingly sub‐horizontal trend that diverges from the mantle array, one hypothesized explanation for which is incorporation of pelagic ± terrigenous sediments in melts [ Reid et al ., ].…”

Section: Introductionmentioning

confidence: 99%

On edge melting under the Colorado Plateau margin

Rudzitis

Reid

Blichert‐Toft

2016

Geochem Geophys Geosyst

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Asthenosphere beneath the relatively thin lithosphere of the Basin and Range province appears to be juxtaposed in step‐like fashion against the Colorado Plateau's thick lithospheric keel. Primary to near‐primary basalts are found above this edge, in the San Francisco‐Morman Mountain volcanic fields, north central Arizona, western USA. We show that at least two distinct peridotite‐dominated mantle end‐members contributed to the origin of the basalts. One has paired Nd and Hf isotopic characteristics that cluster near the mantle array and trace element patterns as expected for melts generated in the asthenosphere, possibly in the presence of garnet. The second has isotopic compositions displaced above the εHf ‐ εNd mantle array which, together with its particular trace element characteristics, indicate contributions from hydrogenous sediments and/or melt (carbonatite or silicate)‐related metasomatism. Melt equilibration temperatures obtained from Si‐ and Mg‐thermobarometry are mostly 1340–1425°C and account for the effects of water (assumed to be 2 wt.%) and estimated CO2 (variable). Melt equilibration depths cluster at the inferred location of the lithosphere‐asthenosphere boundary at ∼70–75 km beneath the southwestern margin of the Colorado Plateau but scatter to somewhat greater values (∼100 km). Melt generation may have initiated in or below the garnet‐spinel facies transition zone by edge‐driven convection and continued as mantle and/or melts upwelled, assimilating and sometimes equilibrating with shallower contaminated mantle, until melts were finally extracted.

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Lower crustal evolution under central Arizona: Sr, Nd and Pb isotopic and geochemical evidence from the mafic xenoliths of Camp Creek

Cited by 71 publications

References 43 publications

Miocene basaltic magmatism in the Goldfield-Superstition volcanic province, central Arizona: Geochemistry, mineralogy, and petrology

Miocene basaltic magmatism in the Goldfield-Superstition volcanic province, central Arizona: Geochemistry, mineralogy, and petrology

Lower crustal and upper mantle xenoliths along the Cheyenne belt and vicinity

On edge melting under the Colorado Plateau margin

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