Relict blocks of massive metabasalt occur within foliated epidote amphibolites that are interlayered in the Paleozoic metapelitic-metapsammitic sequences of the Southalpine basement near Bressanone, Eastern Alps. The original magmatic clinopyroxene–plagioclase–opaque association in metabasalt is variably overprinted by a static alteration, which encompasses a wide spectrum of mineral assemblages. A high-temperature alteration stage is recorded by topotactic overgrowth of Fe-Ti-rich clinopyroxene on primary Fe-poor clinopyroxene, precipitation of datolite and Fe–Ti–rich clinopyroxene (±calcite, chlorite and Co–Ni sulphides) in amygdales, and formation of albite-enriched patches in plagioclase. In places, the primary pyroxenes are partially replaced by kaersutite ± Ti-biotite. In the most altered metabasalts, a probably lower-temperature alteration assemblage, made of Fe-rich and Ti-poor clinopyroxene, calcite, titanian garnet and datolite, replaces the cores of the magmatic pyroxenes. Late veinlets of Fe-rich and Ti-poor clinopyroxene (with minor datolite, garnet and sulphides) are accompanied by further alteration of magmatic clinopyroxenes into chlorite + smectite ± talc, further albitisation of plagioclase, filling of amygdales by datolite ± calcite ± chlorite ± Ca-rich garnet, and precipitation of disseminated sulphides. The alteration sequence recorded in the metabasalts predates the Variscan regional metamorphism recorded by the host amphibolites and is interpreted as being related to circulation of hydrothermal fluids in a submarine continental basin with active magmatism. The lithostratigraphic and structural analogies between the Paleozoic basements of the Southalpine (e.g. Gudon) and Austroalpine (Northern Greywacke Zone) domains of the Eastern Alps, as well as the presence of hydrothermally altered mafic layers in both, suggest that magmatism and associated submarine hydrothermalism in these two domains were related to similar extensional processes affecting the pre-Variscan continental crust, which were possibly synchronous (middle Paleozoic) at the regional scale.
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Research Article|
March 01, 2018
Fossil submarine hydrothermalism in metabasalts from the Gudon (Bressanone) amphibolite (Southalpine basement, Eastern Alps, NE Italy)
Dario Visonà;
Dipartimento di Geoscienze, Università di Padova
, via Gradenigo 6, 35131Padova, Italy
Corresponding author, e-mail: dario.visona@unipd.it
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Christine M. Meyzen;
Christine M. Meyzen
Dipartimento di Geoscienze, Università di Padova
, via Gradenigo 6, 35131Padova, Italy
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Paolo Nimis;
Paolo Nimis
Dipartimento di Geoscienze, Università di Padova
, via Gradenigo 6, 35131Padova, Italy
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Fabrizio Nestola
Fabrizio Nestola
Dipartimento di Geoscienze, Università di Padova
, via Gradenigo 6, 35131Padova, Italy
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Christine M. Meyzen
Dipartimento di Geoscienze, Università di Padova
, via Gradenigo 6, 35131Padova, Italy
Paolo Nimis
Dipartimento di Geoscienze, Università di Padova
, via Gradenigo 6, 35131Padova, Italy
Fabrizio Nestola
Dipartimento di Geoscienze, Università di Padova
, via Gradenigo 6, 35131Padova, Italy
Corresponding author, e-mail: dario.visona@unipd.it
Publisher: Deutsche Mineralogische Gesellschaft, Sociedad Española de Mineralogia, Societá Italiana di Mineralogia e Petrologia, Société Francaise de Minéralogie
Received:
16 Jun 2017
Revision Received:
16 Nov 2017
Accepted:
17 Nov 2017
First Online:
14 Aug 2018
Online ISSN: 1617-4011
Print ISSN: 0935-1221
© 2018 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart
European Journal of Mineralogy (2018) 30 (2): 355–366.
Article history
Received:
16 Jun 2017
Revision Received:
16 Nov 2017
Accepted:
17 Nov 2017
First Online:
14 Aug 2018
Citation
Dario Visonà, Christine M. Meyzen, Paolo Nimis, Fabrizio Nestola; Fossil submarine hydrothermalism in metabasalts from the Gudon (Bressanone) amphibolite (Southalpine basement, Eastern Alps, NE Italy). European Journal of Mineralogy 2018;; 30 (2): 355–366. doi: https://doi.org/10.1127/ejm/2018/0030-2720
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Index Terms/Descriptors
- Alps
- amphibolites
- Bolzano Italy
- Eastern Alps
- Europe
- high temperature
- hydrothermal alteration
- Italy
- major elements
- marine environment
- metabasalt
- metaigneous rocks
- metamorphic rocks
- metamorphism
- metasomatism
- mineral assemblages
- overprinting
- Paleozoic
- relict materials
- Southern Europe
- submarine environment
- temperature
- trace elements
- Trentino-Alto Adige Italy
- Variscan Orogeny
- whole rock
- Chiusa Italy
- Bressanone Italy
- Southalpine
Latitude & Longitude
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