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Geochemical and lead isotope evidence for a mid-ocean ridge type mineralization within a polymetamorphic ophiolite complex (Monte del Forno, North Italy/Switzerland)

Abstract

Major, trace element and Pb isotope investigations show the presence of a mid-ocean ridge-type mineralization within the polymetamorphic Monte del Forno Unit. Detailed analysis of the lithostratigraphy of the amphibolites demonstrates a close similarity to recent oceanic crust: a dyke zone at the bottom, a hydrothermally altered zone with a stockwork-type Fe-Cu-Zn mineralization and a pillow zone at the top. Effects of hydrothermal seafloor alteration are restricted to an approximately 50 m thick horizon. Sulfide mineralization is accompanied by Ca and Sr depletion and Mn and minor Na and Mg enrichments. Mineralogically the horizon distinguishes itself from the unmineralized amphibolites by the presence of chlorite and contact metamorphic magnesio-cummingtonite. The chemical imprint of the hydrothermal seafloor alteration survived a regional greenschist and an upper amphibolite facies contact metamorphism. The MORB signature of the Pb isotopes is preserved in the central parts of the approximately 300 m thick amphibolite sequence. During the regional greenschist facies metamorphism the isotope characteristics of the amphibolites were almost completely changed at the contact to the metasediments. The contact metamorphism of the Bregaglia Intrusion produced no obvious Pb contamination even within amphibolite xenoliths in the granodiorite.
Publication Date:
Nov 01, 1986
Product Type:
Journal Article
Reference Number:
NLN-87-000315; EDB-87-024957
Resource Relation:
Journal Name: Earth Planet. Sci. Lett.; (Netherlands); Journal Volume: 80:3/4
Subject:
54 ENVIRONMENTAL SCIENCES; ALPS; GEOCHEMISTRY; ISOTOPE RATIO; LEAD 204; LEAD 206; LEAD 207; LEAD 208; MINERALS; STRATIGRAPHY; TRACE AMOUNTS; ALPHA DECAY RADIOISOTOPES; CHEMISTRY; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; GEOLOGY; HEAVY NUCLEI; HOURS LIVING RADIOISOTOPES; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; LEAD ISOTOPES; MOUNTAINS; NUCLEI; RADIOISOTOPES; SECONDS LIVING RADIOISOTOPES; STABLE ISOTOPES; YEARS LIVING RADIOISOTOPES; 510101* - Environment, Terrestrial- Basic Studies- Radiometric Techniques- (-1989)
OSTI ID:
6907450
Research Organizations:
Eidgenoessische Technische Hochschule, Zurich, Switzerland. Inst. fuer Mineralogie und Petrographie; Eidgenoessische Technische Hochschule, Zurich, Switzerland. Inst. fuer Kristallographie und Petrographie
Country of Origin:
Netherlands
Language:
English
Other Identifying Numbers:
Journal ID: CODEN: EPSLA
Submitting Site:
NLN
Size:
Pages: 252-264
Announcement Date:

Citation Formats

Peretti, A, and Koeppel, V. Geochemical and lead isotope evidence for a mid-ocean ridge type mineralization within a polymetamorphic ophiolite complex (Monte del Forno, North Italy/Switzerland). Netherlands: N. p., 1986. Web. doi:10.1016/0012-821X(86)90109-3.
Peretti, A, & Koeppel, V. Geochemical and lead isotope evidence for a mid-ocean ridge type mineralization within a polymetamorphic ophiolite complex (Monte del Forno, North Italy/Switzerland). Netherlands. doi:10.1016/0012-821X(86)90109-3.
Peretti, A, and Koeppel, V. 1986. "Geochemical and lead isotope evidence for a mid-ocean ridge type mineralization within a polymetamorphic ophiolite complex (Monte del Forno, North Italy/Switzerland)." Netherlands. doi:10.1016/0012-821X(86)90109-3. https://www.osti.gov/servlets/purl/10.1016/0012-821X(86)90109-3.
@misc{etde_6907450,
title = {Geochemical and lead isotope evidence for a mid-ocean ridge type mineralization within a polymetamorphic ophiolite complex (Monte del Forno, North Italy/Switzerland)}
author = {Peretti, A, and Koeppel, V}
abstractNote = {Major, trace element and Pb isotope investigations show the presence of a mid-ocean ridge-type mineralization within the polymetamorphic Monte del Forno Unit. Detailed analysis of the lithostratigraphy of the amphibolites demonstrates a close similarity to recent oceanic crust: a dyke zone at the bottom, a hydrothermally altered zone with a stockwork-type Fe-Cu-Zn mineralization and a pillow zone at the top. Effects of hydrothermal seafloor alteration are restricted to an approximately 50 m thick horizon. Sulfide mineralization is accompanied by Ca and Sr depletion and Mn and minor Na and Mg enrichments. Mineralogically the horizon distinguishes itself from the unmineralized amphibolites by the presence of chlorite and contact metamorphic magnesio-cummingtonite. The chemical imprint of the hydrothermal seafloor alteration survived a regional greenschist and an upper amphibolite facies contact metamorphism. The MORB signature of the Pb isotopes is preserved in the central parts of the approximately 300 m thick amphibolite sequence. During the regional greenschist facies metamorphism the isotope characteristics of the amphibolites were almost completely changed at the contact to the metasediments. The contact metamorphism of the Bregaglia Intrusion produced no obvious Pb contamination even within amphibolite xenoliths in the granodiorite.}
doi = {10.1016/0012-821X(86)90109-3}
journal = {Earth Planet. Sci. Lett.; (Netherlands)}
volume = {80:3/4}
journal type = {AC}
place = {Netherlands}
year = {1986}
month = {Nov}
}