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Lithosphere thickness controls continental basalt compositions; an illustration using Cenozoic basalts from eastern China

Guo Pengyuan, Niu Yaoling, Sun Pu, Gong Hongmei and Wang Xiaohong
Lithosphere thickness controls continental basalt compositions; an illustration using Cenozoic basalts from eastern China
Geology (Boulder) (November 2019) 48 (2): 128-133

Abstract

Recent studies demonstrate that lithosphere thickness variation exerts the primary control on global seafloor basalt compositions. If the mechanism of such control, i.e., the lid effect, is indeed at work, lithosphere thickness variation must also influence basaltic compositions in continental settings. To test this hypothesis, we chose to study Cenozoic basalts in eastern continental China over a distance of approximately 260 km along a southeast-to-northwest traverse with a steep topographic gradient ( approximately 500 to approximately 1500 m above sea level) mirrored with a steep lithospheric thickness gradient ( approximately 80 to approximately 120 km). The basalts erupted on the thinned lithosphere to the east are characterized by lower pressure (e.g., higher Si (sub 72) , lower Mg (sub 72) , Fe (sub 72) , and [Sm/Yb]N; subscript "72" refers to corresponding oxides corrected for fractionation effect to Mg# = 72; N-primitive mantle normalized) and higher extent (e.g., low Ti (sub 72) , P (sub 72) , K (sub 72) , Rb, Ba, Th, and ratios of more- to less-incompatible elements such as [La/Sm]N, Ba/Zr, and Zr/Yb) of melting than basalts erupted on the thickened lithosphere to the west. Importantly, these geochemical parameters all show significant correlations with both lithosphere thickness and topographic elevation. These first-order observations are a straightforward manifestation of the lid effect. Lithospheric contamination and mantle-source compositional variation can indeed contribute to the compositional variability of these continental basalts, but these latter effects are averaged out and are overshadowed by the lid effect. This finding emphasizes the importance of evaluating the lid effect before interpreting the petrogenesis of continental basalts and mantle dynamics. Our results also indicate that the continental surface elevation is isostatically balanced above a mantle depth that is deeper than the lithosphere-asthenosphere boundary.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 48
Serial Issue: 2
Title: Lithosphere thickness controls continental basalt compositions; an illustration using Cenozoic basalts from eastern China
Affiliation: Chinese Academy of Sciences, Institute of Oceanology, Key Laboratory of Marine Geology and Environment, Qingdao, China
Pages: 128-133
Published: 20191122
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 28
Accession Number: 2020-000552
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2020xxx
Illustration Description: illus. incl. geol. sketch map
N41°49'60" - N44°00'00", E115°40'00" - E120°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 202001
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