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In search for the missing arc root of the Southern California Batholith: P-T-t evolution of upper mantle xenoliths of the Colorado Plateau Transition Zone

Rautela, Ojashvi and Chapman, Alan D. and Shields, Jessie E. and Ducea, Mihai N. and Lee, Cin-Ty and Jiang, Hehe and Saleeby, Jason (2020) In search for the missing arc root of the Southern California Batholith: P-T-t evolution of upper mantle xenoliths of the Colorado Plateau Transition Zone. Earth and Planetary Science Letters, 547 . Art. No. 116447. ISSN 0012-821X. doi:10.1016/j.epsl.2020.116447.

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Xenolith and seismic studies provide evidence for tectonic erosion and eastward displacement of lower crust-subcontinental mantle lithosphere (LC-SCML) underlying the Mojave Desert Region (i.e. southern California batholith (SCB)). Intensified traction associated with the Late Cretaceous flattening of the subducting Farallon plate, responsible for deforming the SW U.S., likely played a key role in “bulldozing” the tectonically eroded LC-SCML ∼500 km eastwards, to underneath the Colorado Plateau Transition Zone (CPTZ) and further inboard. The garnet clinopyroxenite xenoliths from two CPTZ localities, Chino Valley and Camp Creek (central Arizona), provide a rare glimpse of the material underlying the CPTZ. Thermodynamic modeling, in addition to major and trace element thermobarometry, suggests that the xenoliths experienced peak conditions of equilibration at 600-900 °C and 12-28 kbar. These peak conditions, along with the composition of the xenoliths (type “B” garnet and diopsidic clinopyroxene) strongly suggest a continental arc residue (“arclogite”), rather than a lower plate subduction (“eclogite”), origin. A bimodal zircon U-Pb age distribution with peaks at ca. 75 and 150 Ma, and a Jurassic Sm-Nd garnet age (154 ± 16 Ma, with initial εNd value of +8) overlaps eastern SCB pluton ages and suggests a consanguineous relationship. Cenozoic zircon U-Pb ages, REE geochemistry of zircon grains, and partially re-equilibrated Sm-Nd garnet ages indicate that displaced arclogite remained at elevated PT conditions (>700 °C) for 10s of Myr following its dispersal until late Oligocene entrainment in host latite. With a ∼100 Myr long thermal history overlapping that of the SCB and the CPTZ, these assemblages also contain evidence for late-stage hydration (e.g. secondary amphibole), potentially driven by de-watering of the Laramide slab. In light of these results, we suggest that the CPTZ arclogite originates from beneath the eastern half of the SCB, where it began forming in Late Jurassic time as mafic keel to continental arc magmas. The displacement and re-affixation of the arclogites further inboard during the Late Cretaceous flat slab subduction, might have contributed to the tectonic stability of the Colorado Plateau relative to adjacent geologic provinces through Laramide time and likely preconditioned the region to Cenozoic tectonism, e.g. present-day delamination beneath the plateau, high-magnitude extension and formation of metamorphic core complexes.

Item Type:Article
Related URLs:
URLURL TypeDescription
Chapman, Alan D.0000-0001-9865-603X
Ducea, Mihai N.0000-0002-5322-0782
Lee, Cin-Ty0000-0002-3586-0110
Jiang, Hehe0000-0002-5767-0043
Additional Information:© 2020 Elsevier B.V. Received 13 January 2020, Revised 24 June 2020, Accepted 28 June 2020, Available online 15 July 2020. This effort benefited from assistance by D. Abboud, B. Hunter and J. Thole at Macalester College; A. von der Handt at University of Minnesota; and discussions with S. Esperança and D. Smith. This work was supported by NSF grants EAR-1524768 (to ADC) and EAR-1725002 (to MND) and Romanian UEFISCDI project PN-III-P4-ID-PCCF-2016-0014 (to MND). We appreciate constructive reviews by Richard Carlson and Marty Grove. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding AgencyGrant Number
Unitatea Executiva pentru Finantarea Invatamantului Superior, a Cercetarii, Dezvoltarii si InovariiPN-III-P4-ID-PCCF-2016-0014
Subject Keywords:Laramide; Colorado Plateau Transition Zone; Southern California Batholith; Cordilleran tectonics; garnet-clinopyroxenite; P-T-t evolution
Record Number:CaltechAUTHORS:20200716-092537880
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Official Citation:Ojashvi Rautela, Alan D. Chapman, Jessie E. Shields, Mihai N. Ducea, Cin-Ty Lee, Hehe Jiang, Jason Saleeby, In search for the missing arc root of the Southern California Batholith: P-T-t evolution of upper mantle xenoliths of the Colorado Plateau Transition Zone, Earth and Planetary Science Letters, Volume 547, 2020, 116447, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104398
Deposited By: Tony Diaz
Deposited On:16 Jul 2020 17:39
Last Modified:16 Nov 2021 18:31

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