A study of uranium favorability of Cenozoic sedimentary rocks, Basin and Range Province, Arizona: Part I. General geology and chronology of pre-late Miocene Cenozoic sedimentary rocks

Scarborough, R.B.; Wilt, Jan C.

doi:10.3133/ofr791429

Cited by 23 publications

(42 citation statements)

References 5 publications

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“…[Scarborough and Wilt, 1979;Rehrig et al, 1980;Shafiqullah et al, 1980]. Dates considered to be tinreliable are as follows: A feldspar K-Ar date of 16.6_+0.4 from rhyolitic rocks in the Vulture Mountains is probably spurious; the sampled rhyolite directly overlies basalt dated at 19.9_+0.…”

mentioning

confidence: 99%

Spatial and temporal relationships between mid‐Tertiary magmatism and extension in southwestern Arizona

Spencer¹,

Richard²,

Reynolds³

et al. 1995

J. Geophys. Res.

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Cenozoic magmatism in southwestern Arizona, which is within the Basin and Range tectonic province, occurred almost entirely between 15 and 25 Ma. Volcanic rocks typically consist, in ascending order, of (1) a thin sequence of mafic to intermediate lava flows, (2) voluminous felsic lava flows and pyroclastic rocks with minor to moderate amounts of intermediate to mafic lava flows, and (3) basalt and andesite. Volcanic rock sequences rest disconformably on pre‐Tertiary bedrock in most areas but locally overlie substantial coarse clastic debris that was deposited immediately before and during earliest magmatism. Prevolcanic clastic debris is interpreted as a consequence of local early normal faulting. In most regions, tilting related to extension began later and occurred during or after eruption of felsic volcanic rocks and before the end of younger mafic volcanism. Extension generally ended before about 17 Ma except in a northwest trending belt adjacent to the relatively unfaulted and topographically elevated Transition Zone tectonic province which is adjacent to the Colorado Plateau. Rapid cooling of metamorphic core complexes and tilting of young basalts and coarse clastic rocks continued in this belt until as recently as 11 Ma. Extension was extreme in this belt, whereas it was generally moderate to slight in other parts of southwestern Arizona. Large‐magnitude extension was not associated with areas of greatest igneous activity, and rapid cooling and exhumation of core complexes postdated local magmatism. These relationships are inconsistent with theories that relate genesis of metamorphic core complexes to magma intrusion in the upper crust. Except for young extension in this northwest trending belt, there are no apparent regional migration trends for either magmatism or extension within southwestern Arizona. Lack of substantial extension before magmatism and general lack of magmatism during youngest extension are inconsistent with the hypothesis that magmatism was the product of decompression melting during lithospheric extension. The long duration and large magnitude of extension adjacent to the Transition Zone tectonic province and within an area of earlier crustal thickening are consistent with the hypothesis that extension was driven by the gravitational potential energy of elevated land mass and crustal roots. Regional magmatic heating apparently weakened the lithosphere and triggered extension but did not control extension locally.

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mentioning

confidence: 99%

Spatial and temporal relationships between mid‐Tertiary magmatism and extension in southwestern Arizona

Spencer¹,

Richard²,

Reynolds³

et al. 1995

J. Geophys. Res.

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“…The maximum depositional age of unit Tcb is 22.6 ± 0.2 Ma based on the 206 Pb/ 238 U age of the underlying rhyolitic ash flow tuff (Unit Tt) [ Reynolds and Spencer , ] (Figure ). Previous age determinations for unit Tt include a K‐Ar biotite age of 23.9 ± 0.9 Ma [ Brooks , ] and a whole‐rock K‐Ar age of 15.8 ± 0.4 Ma [ Scarborough and Wilt , ]. Pervasive K‐metasomatism within upper‐plate rocks in the region [ Roddy et al ., ] likely accounts for the unreliable K‐Ar ages.…”

Section: Correlation Of Footwall and Hanging Wall Unitsmentioning

confidence: 99%

Miocene slip history of the Eagle Eye detachment fault, Harquahala Mountains metamorphic core complex, west-central Arizona

2016

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The structural and thermal evolution of major low‐angle normal faults in the Colorado River extensional corridor has been a controversial topic since the pioneering studies of metamorphic core complexes in the early 1980s. We present new geo‐thermochronometry data from the Harquahala Mountains in west‐central Arizona to determine the timing of extension, displacement magnitude, and slip rates along the Eagle Eye detachment fault (EED) during large‐magnitude Miocene extension. Zircon and apatite (U‐Th)/He data (ZHe and AHe, respectively) from 31 samples along a ~55 km extension‐parallel transect indicate active slip along the EED occurred between ~21 ± 1 Ma and ~14 Ma. The spatial extent of ZHe ages and exhumation of the zircon partial retention zone indicated ~44 ± 2 km of total displacement, whereas lithologic similarity and identical U‐Pb ages between correlated footwall rocks in the Little Harquahala Mountains and breccia clasts at Bullard Peak in the NE Harcuvar Mountains indicated ~43–45 km of displacement across the EED. AHe and ZHe data indicated slip rates of ~6.7 + 7.8/−2.3 km/Myr, and ~6.6 + 7.1/−2.0 km/Myr, respectively, both consistent with the duration and displacement estimates. The EED initiated as a listric fault with an ~34 ± 9° dip that decreased to ~13 ± 5° below ~7 km depth. Secondary breakaway development and footwall exposure occurred by ~17 Ma, during active EED slip. Lithologic and geo‐thermochronometric offset constraints show excellent agreement and provided a rare opportunity to fully resolve the timing, rates, and total displacement magnitudes along a major continental detachment fault.

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“…In the Muggins Mountains, located about 45 km west of the northwest corner of the quadrangle, uranium exploration has focused on vitric tuff and tuffaceous lacustrine siltstone which form the lower member of the late Oligocene(?) to Early Miocene Kinter Formation (Smith and others, 1984;Scarborough, 1979;Scarborough and Wilt, 1979;Olmsted and others, 1973). The edge of area E10 in the quadrangle (pi.…”

Section: Evaluation Of Evaporite Depositsmentioning

confidence: 99%

Mineral resource assessment of the Ajo and Lukeville 1° by 2° quadrangles, Arizona

Peterson¹,

Cox²,

Gray³

1985

Open-File Report

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A study of uranium favorability of Cenozoic sedimentary rocks, Basin and Range Province, Arizona: Part I. General geology and chronology of pre-late Miocene Cenozoic sedimentary rocks

Cited by 23 publications

References 5 publications

Spatial and temporal relationships between mid‐Tertiary magmatism and extension in southwestern Arizona

Spatial and temporal relationships between mid‐Tertiary magmatism and extension in southwestern Arizona

Miocene slip history of the Eagle Eye detachment fault, Harquahala Mountains metamorphic core complex, west-central Arizona

Mineral resource assessment of the Ajo and Lukeville 1° by 2° quadrangles, Arizona

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