DOI: 10.1016/j.epsl.2020.116447
论文题名: 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
作者: Rautela O. ; Chapman A.D. ; Shields J.E. ; Ducea M.N. ; Lee C.-T. ; Jiang H. ; Saleeby J.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 547 语种: 英语
中文关键词: Colorado Plateau Transition Zone
; Cordilleran tectonics
; garnet-clinopyroxenite
; Laramide
; P-T-t evolution
; Southern California Batholith
英文关键词: Binary alloys
; Garnets
; Igneous rocks
; Metamorphic rocks
; Samarium alloys
; Silicate minerals
; Structural geology
; Tectonics
; Trace elements
; Zircon
; Flat-slab subductions
; Major and trace elements
; Metamorphic core complex
; Southern California
; Subcontinental mantle
; Tectonic erosion
; Tectonic stability
; Thermodynamic model
; Lead alloys
; batholith
; continental arc
; displacement
; lithospheric structure
; lower crust
; magma
; P-T conditions
; tectonic evolution
; transition zone
; upper mantle
; xenolith
; Arizona
; Colorado Plateau
; Mojave Desert
; United States
英文摘要: 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. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165227
Appears in Collections: 气候变化与战略
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作者单位: Geology Department, Macalester College, St. Paul, MN 55105, United States; Department of Earth and Environmental Sciences, California State University, Fresno, CA 93740, United States; Department of Geosciences, University of Arizona, Tucson, AZ 85721, United States; Faculty of Geology and Geophysics, University of Bucharest, Bucharest, 010041, Romania; Department of Earth Science, Rice University, Houston, TX 77005, United States; Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States
Recommended Citation:
Rautela O.,Chapman A.D.,Shields J.E.,et al. 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[J]. Earth and Planetary Science Letters,2020-01-01,547