Evidence of South American lithosphere mantle beneath the Chile mid-ocean ridge

被引:5
|
作者
Mallick, Soumen [1 ]
Kuhl, Sophie E. [1 ]
Saal, Alberto E. [1 ]
Klein, Emily M. [2 ]
Bach, Wolfgang [3 ]
Monteleone, Brian D. [4 ]
Boesenberg, Joseph S. [1 ]
机构
[1] Brown Univ, Dept Earth Environm & Planetary Sci, 324 Brook St,Box 1846, Providence, RI 02912 USA
[2] Div Earth & Ocean Sci, 9 Circuit Dr,Box 90328, Durham, NC 27708 USA
[3] Univ Bremen, Dept Geosci, Klagenfurter Str 2, D-28359 Bremen, Germany
[4] Woods Hole Oceanog Inst, Mail Stop 23,266 Woods Hole Rd, Woods Hole, MA 02543 USA
关键词
Chile mid -ocean ridge; slab window; mantle flow; lithosphere delamination; MID-ATLANTIC RIDGE; TRACE-ELEMENT; ISOTOPIC EVIDENCE; CONTINENTAL LITHOSPHERE; GEOCHEMICAL VARIATIONS; HETEROGENEITY BENEATH; MELT INCLUSIONS; VOLCANIC ZONE; PATAGONIA; SUBDUCTION;
D O I
10.1016/j.epsl.2023.118320
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Numerous geochemical studies on mid-ocean ridge basalts have established the presence of both compositional and lithological heterogeneities in the upper mantle. These studies have successfully constrained the composition and age of the chemical heterogeneities within the Earth's upper mantle. However, the origin of those heterogeneities remains highly debated. The Chile Mid-Ocean Ridge in the southeast Pacific Ocean, located far away from any hotspot, is colliding and subducting under the South America plate promoting the formation of a slab window. Comprehensive geochemical data (major, trace, volatile element contents and Sr, Nd, Hf and Pb isotope ratios) on Chile Ridge submarine glasses collected over the 1000 km ridge length demonstrate significant mantle compositional variability. Four main mantle components have been recognized: the typical Pacific MORB mantle, an enriched mantle (e.g., EM-1), a Subduction Modified mantle, and an anciently depleted mantle with unusually high Hf isotope ratios. Surprisingly, despite the large compositional variability, all glasses - including those with a subduction signature - have volatile-refractory element ratios within the range of the Pacific normal MORB. We propose that the Patagonia sub-continental lithospheric mantle, variably metasomatized since the Early Paleozoic, is eroded and incorporated into an asthenosphere with a south Atlantic MORB mantle composition that is flowing westward across the slab window from South America to the Chile Ridge. This scenario contrasts with a well-accepted geodynamic model that predicts the opposite direction of mantle flow. We speculate that the westward mantle flow across the slab window might be a counter -flow response to the opening of the Drake passage and the eastward movement of Pacific mantle since-30 Ma ago.& COPY; 2023 Elsevier B.V. All rights reserved.
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页数:12
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