Geochemistry of oceanic carbonatites compared with continental carbonatites: Mantle recycling of oceanic crustal carbonate

Hoernle, Kaj, Tilton, George, Le Bas, Mike J., Duggen, Svend and Garbe-Schönberg, C.-Dieter (2001) Geochemistry of oceanic carbonatites compared with continental carbonatites: Mantle recycling of oceanic crustal carbonate Contributions to Mineralogy and Petrology, 142 . pp. 520-542. DOI 10.1007/s004100100308.

[img] Text
art_10.1007_s004100100308.pdf - Published Version
Restricted to Registered users only

Download (394Kb) | Contact

Supplementary data:


Major and trace element and Sr–Nd–Pb–O–C isotopic compositions are presented for carbonatites from the Cape Verde (Brava, Fogo, Sáo Tiago, Maio and Sáo Vicente) and Canary (Fuerteventura) Islands. Carbonatites show pronounced enrichment in Ba, Th, REE, Sr and Pb in comparison to most silicate volcanic rocks and relative depletion in Ti, Zr, Hf, K and Rb. Calcio (calcitic)-carbonatites have primary (mantle-like) stable isotopic compositions and radiogenic isotopic compositions similar to HIMU-type ocean island basalts. Cape Verde carbonatites, however, have more radiogenic Pb isotope ratios (e.g. 206Pb/204Pb=19.3–20.4) than reported for silicate volcanic rocks from these islands (18.7–19.9; Gerlach et al. 1988; Kokfelt 1998). We interpret calcio-carbonatites to be derived from the melting of recycled carbonated oceanic crust (eclogite) with a recycling age of ~1.6 Ga. Because of the degree of recrystallization, replacement of calcite by secondary dolomite and elevated ∂13C and ∂18O, the major and trace element compositions of the magnesio (dolomitic)-carbonatites are likely to reflect secondary processes. Compared with Cape Verde calcio-carbonatites, the less radiogenic Nd and Pb isotopic ratios and the negative Δ7/4 of the magnesio-carbonatites (also observed in silicate volcanic rocks from the Canary and Cape Verde Islands) cannot be explained through secondary processes or through the assimilation of Cape Verde crust. These isotopic characteristics require the involvement of a mantle component that has thus far only been found in the Smoky Butte lamproites from Montana, which are believed to be derived from subcontinental lithospheric sources. Continental carbonatites show much greater variation in radiogenic isotopic composition than oceanic carbonatites, requiring a HIMU-like component similar to that observed in the oceanic carbonatites and enriched components. We interpret the enriched components to be Phanerozoic through Proterozoic marine carbonate (e.g. limestone) recycled through shallow, subcontinental–lithospheric–mantle and deep, lower-mantle sources.

Document Type: Article
Research affiliation: OceanRep > SFB 574 > C2
Kiel University
OceanRep > SFB 574
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor
OceanRep > SFB 574 > B4
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
Refereed: Yes
DOI etc.: 10.1007/s004100100308
ISSN: 0010-7999
Projects: SFB574
Contribution Number:
SFB 5743
Date Deposited: 07 Apr 2010 11:42
Last Modified: 21 Sep 2016 11:20

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...