File Download
  Links for fulltext
     (May Require Subscription)
  • Find via Find It@HKUL
Supplementary

Conference Paper: Possible cold subduction initiation beneath a continental margin in Calabria, Southern Italy

TitlePossible cold subduction initiation beneath a continental margin in Calabria, Southern Italy
Authors
Issue Date2010
PublisherGeological Society of America.
Citation
The 2010 Annual Meeting of the Geological Society of America (GSA), Denver, CO., 31 October-3 November 2010. In Geological Society of America Abstracts with Programs, 2010, v. 42 n. 5, p. 678 How to Cite?
AbstractIn some intraoceanic settings, a new subduction zone is thought to initiate in young and hot oceanic lithosphere, leaving a distinct high-pressure, high-temperature sheet, or metamorphic sole, at the base of the upper plate ophiolite (“hot initiation”). As this involves subduction of very young crust, the igneous protolith and amphibolite-facies metamorphic overprint have similar ages. This HT event is sometimes followed by a blueschist-facies overprint, as continuing subduction lowers the geothermal gradient. Several cases are known from around the world. In contrast, there are no known examples from the rock record of subduction initiation beneath a continental margin. This may be because subduction along continental margins begins with, and beneath, old and cold crust, in low geothermal gradient settings. These cool conditions prevent formation of the distinctive HT event seen in intraoceanic settings, making recognition of this process difficult. Instead, the first evidence of subduction zone metamorphism may be a blueschist-facies metamorphism of crust that was very old, and cold, at the time of subduction (“cold initiation”). The Cenozoic accretionary wedge in Northern Calabria, Southern Italy, emplaced beneath the former continental margin of the Corsica-Sardinia microplate, meets these criteria. The structurally highest unit affected by later HP Alpine metamorphism, the blueschist-overprinted garnet-amphibolite Zangarona Schist, has given an amphibole Ar/Ar age of 302±4 Ma, consistent with a late Hercynian metamorphic event. Below it, the blueschist-facies Tethyan ophiolite unit is through to be Jurassic in age, based on the overlying Calpionella limestone. Since both units were affected by a blueschist-facies Alpine event, estimated by other workers to be 40 Ma in age, subduction must have begun in crust at least 100 Ma old. Initiation of subduction in such old crust, plus the lack of an initial HT Alpine event, suggests that subduction began in relatively cold conditions, unlike the hot subduction initiation sometimes seen in intraoceanic settings. Preservation of evidence for subduction initiation here may be aided by the unique lack of continental collision in this part of the Alpine Orogen.
DescriptionSession no. 291 - Initiation and Termination of Subduction: Rock Record, Geodynamic Models, Modern Plate Boundaries II: paper no. 291-5
Persistent Identifierhttp://hdl.handle.net/10722/153306
ISSN

 

DC FieldValueLanguage
dc.contributor.authorShimabukuro, DHen_US
dc.contributor.authorWakabayashi, Jen_US
dc.contributor.authorAlvarez, Wen_US
dc.contributor.authorChang, Sen_US
dc.date.accessioned2012-07-16T10:05:31Z-
dc.date.available2012-07-16T10:05:31Z-
dc.date.issued2010en_US
dc.identifier.citationThe 2010 Annual Meeting of the Geological Society of America (GSA), Denver, CO., 31 October-3 November 2010. In Geological Society of America Abstracts with Programs, 2010, v. 42 n. 5, p. 678en_US
dc.identifier.issn0016-7592-
dc.identifier.urihttp://hdl.handle.net/10722/153306-
dc.descriptionSession no. 291 - Initiation and Termination of Subduction: Rock Record, Geodynamic Models, Modern Plate Boundaries II: paper no. 291-5-
dc.description.abstractIn some intraoceanic settings, a new subduction zone is thought to initiate in young and hot oceanic lithosphere, leaving a distinct high-pressure, high-temperature sheet, or metamorphic sole, at the base of the upper plate ophiolite (“hot initiation”). As this involves subduction of very young crust, the igneous protolith and amphibolite-facies metamorphic overprint have similar ages. This HT event is sometimes followed by a blueschist-facies overprint, as continuing subduction lowers the geothermal gradient. Several cases are known from around the world. In contrast, there are no known examples from the rock record of subduction initiation beneath a continental margin. This may be because subduction along continental margins begins with, and beneath, old and cold crust, in low geothermal gradient settings. These cool conditions prevent formation of the distinctive HT event seen in intraoceanic settings, making recognition of this process difficult. Instead, the first evidence of subduction zone metamorphism may be a blueschist-facies metamorphism of crust that was very old, and cold, at the time of subduction (“cold initiation”). The Cenozoic accretionary wedge in Northern Calabria, Southern Italy, emplaced beneath the former continental margin of the Corsica-Sardinia microplate, meets these criteria. The structurally highest unit affected by later HP Alpine metamorphism, the blueschist-overprinted garnet-amphibolite Zangarona Schist, has given an amphibole Ar/Ar age of 302±4 Ma, consistent with a late Hercynian metamorphic event. Below it, the blueschist-facies Tethyan ophiolite unit is through to be Jurassic in age, based on the overlying Calpionella limestone. Since both units were affected by a blueschist-facies Alpine event, estimated by other workers to be 40 Ma in age, subduction must have begun in crust at least 100 Ma old. Initiation of subduction in such old crust, plus the lack of an initial HT Alpine event, suggests that subduction began in relatively cold conditions, unlike the hot subduction initiation sometimes seen in intraoceanic settings. Preservation of evidence for subduction initiation here may be aided by the unique lack of continental collision in this part of the Alpine Orogen.-
dc.languageengen_US
dc.publisherGeological Society of America.-
dc.relation.ispartofGeological Society of America Abstracts with Programsen_US
dc.titlePossible cold subduction initiation beneath a continental margin in Calabria, Southern Italyen_US
dc.typeConference_Paperen_US
dc.identifier.emailChang, S: suchin@hku.hken_US
dc.identifier.authorityChang, S=rp01478en_US
dc.description.naturelink_to_OA_fulltext-
dc.identifier.hkuros200864en_US
dc.identifier.volume42-
dc.identifier.issue5-
dc.identifier.spage678-
dc.identifier.epage678-
dc.publisher.placeUnited States-

Export via OAI-PMH Interface in XML Formats


OR


Export to Other Non-XML Formats