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Uplift of the southeastern Australian lithosphere; thermal-tectonic evolution of garnet pyroxenite xenoliths from western Victoria

Jianggu Lu, Xiong Qing, William L. Griffin, Zheng Jianping, Huang Jinxiang, Suzanne Y. O'Reilly, Takako Satsukawa and Norman J. Pearson
Uplift of the southeastern Australian lithosphere; thermal-tectonic evolution of garnet pyroxenite xenoliths from western Victoria (in The crust-mantle and lithosphere-asthenosphere boundaries; insights from xenoliths, orogenic deep sections, and geophysical studies, Gianluca Bianchini (editor), Jean-Louis Bodinier (editor), Roberto Braga (editor) and Marjorie Wilson (editor))
Special Paper - Geological Society of America (March 2017) 526: 27-48

Abstract

Detailed petrography, microstructure, and geochemistry of garnet pyroxenite xenoliths in Holocene basanite tuffs from maars at Lakes Bullenmerri and Gnotuk (western Victoria, southeastern Australia) have been used to track their igneous and metamorphic history, enabling the reconstruction of the thermal-tectonic evolution of the lithospheric mantle. The exsolution of orthopyroxene and garnet and rare spinel, plagioclase, and ilmenite from complex clinopyroxene megacrysts suggests that the xenoliths originally were clinopyroxene-dominant cumulates associated with minor garnet, orthopyroxene, or spinel. The compositions of exsolved phases and their host clinopyroxene were reintegrated using measured modal proportions to show that the primary clinopyroxene was enriched in Al (sub 2) O (sub 3) (5.53-13.63 wt%) and crystallized at approximately 1300-1500 degrees C and 16-30 kbar. These cumulates then underwent extensive exsolution, recrystallization, and reaction during cooling, and finally equilibrated at approximately 950-1100 degrees C and 12-18 kbar before entrainment in the basanites. Rare earth element (REE) thermobarometry of garnets and coexisting clinopyroxenes preserves evidence of an intermediate stage (1032 degrees C and 21 kbar). These results imply that the protoliths of the garnet pyroxenite formed at a range of depths from approximately 50 to 100 km, and then during or shortly after cooling, they were tectonically emplaced to higher levels ( approximately 40-60 km; i.e., uplifted by at least 10-20 km) along the prevailing geotherm. This uplift may have been connected with lithosphere-scale faulting during the Paleozoic orogeny, or during Mesozoic-Cenozoic rifting of eastern Australia.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 526
Title: Uplift of the southeastern Australian lithosphere; thermal-tectonic evolution of garnet pyroxenite xenoliths from western Victoria
Title: The crust-mantle and lithosphere-asthenosphere boundaries; insights from xenoliths, orogenic deep sections, and geophysical studies
Author(s): Lu, JiangguXiong QingGriffin, William L.Zheng JianpingHuang JinxiangO'Reilly, Suzanne Y.Satsukawa, TakakoPearson, Norman J.
Author(s): Bianchini, Gianlucaeditor
Author(s): Bodinier, Jean-Louiseditor
Author(s): Braga, Robertoeditor
Author(s): Wilson, Marjorieeditor
Affiliation: China University of Geosciences, School of Earth Sciences, Wuhan, China
Pages: 27-48
Published: 20170323
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Number of pages: 22
References: 84
Accession Number: 2017-035073
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, sketch map
S39°00'00" - S34°00'00", E140°00'00" - E150°00'00"
Secondary Affiliation: Macquarie University, AUS, AustraliaKyoto University, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201720
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