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Neoproterozoic continental arc magmatism in west-central Madagascar

Michael J. Handke, Robert D. Tucker and Lewis D. Ashwal
Neoproterozoic continental arc magmatism in west-central Madagascar
Geology (Boulder) (April 1999) 27 (4): 351-354


Published geologic maps, regional geological relations, and new U-Pb ages for intrusive igneous rocks in west-central Madagascar define a 450-km-long belt of rocks emplaced in middle Neoproterozoic time. We report precise U-Pb zircon and baddeleyite ages for 11 coeval gabbro and granitoid plutons from the Itremo region, located in the southern part of this belt. The ages for all gabbroic and granitic plutons and deformed equivalents define an approximately 25 m.y. period of magmatic activity between 804 and 779 Ma (at maximum uncertainty). Granitoids intrusive into the Quartzo-Schisto-Calcaire series provide a minimum depositional age of 791 Ma for this Mesoproterozoic platformal sedimentary sequence. Our results, combined with other recent U-Pb age determinations, define a belt of plutonic rocks in west-central Madagascar emplaced between 804 and 776 Ma. We propose that these middle Neoproterozoic rocks constitute the root of a continental magmatic arc emplaced at the time of, or slightly preceding, the breakup of the Rodinian supercontinent. Neoproterozoic plate reconstructions place Madagascar on the putative margin of Rodinia, and therefore the plutonic belt in west-central Madagascar provides important constraints on the timing and extent of middle Neoproterozoic tectonic events in Rodinia and the critical period of Rodinia's transformation into Gondwana.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 27
Serial Issue: 4
Title: Neoproterozoic continental arc magmatism in west-central Madagascar
Affiliation: Washington University, Department of Earth and Planetary Sciences, Saint Louis, MO, United States
Pages: 351-354
Published: 199904
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 28
Accession Number: 1999-034178
Categories: StratigraphyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
S25°40'00" - S11°52'00", E43°00'00" - E50°30'00"
Secondary Affiliation: Rand Afrikaans University, ZAF, South Africa
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: 199912
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