Platinum and palladium in the Ivrea-Verbano basic complex, Western Alps, Italy

Ferrario, A.; Garuti, Giorgio; Sighinolfi, G. P.

doi:10.2113/gsecongeo.77.6.1548

Cited by 20 publications

(13 citation statements)

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“…A further limit to the amount of contamination could be provided by the still LREE depleted pattern (Sm/Nd = 0.336). Thin layers ofmetasediment occurring within the LLG (Ferrario et al 1982) perhaps lend support to the contamination hypothesis.…”

Section: Isotopic Compositionmentioning

confidence: 78%

“…The significance of these lenses is not known and it is possible that they indicate strong isoclinal folding or thrusting. Detailed descriptions of the stratigraphy, mineralogy and mineral chemistry of the layered series are given in Rivalenti et al (1975( , 1981a( , 1981b( , 1984( ), Ferrario et al (1982 and Sills (1984). In this work we review the overall chemistry of the layered series and present isotope analyses.…”

Section: Lower Layered Group (Llg) Petrography and Mineral Chemistrymentioning

confidence: 99%

“…(4) A prominent layer, 50-100 m thick, of granulite-facies metasediment which separates the LLG and MLG from more homogeneous gabbros (Ferrario et al 1982). …”

Section: Geological Settingmentioning

confidence: 99%

“…The LLG is quite strongly deformed with a subvertical foliation parallel to the layering. There are several concordant lenses of granulite-facies metasediment within the LLG and these are often adjacent to nickeliferous pyroxenites (Ferrario et al 1982). The significance of these lenses is not known and it is possible that they indicate strong isoclinal folding or thrusting.…”

Section: Lower Layered Group (Llg) Petrography and Mineral Chemistrymentioning

confidence: 99%

“…Cumulates like the LLG are only found adjacent to the Balmuccia peridotite in Val Sesia, and to the south of Val Strona near the Insubric line (Ferrario et al 1982; Fig. 1) and are separated from the main gabbro-diorite body by a layer of metasediment.…”

Section: Composition Of Parental Liquidmentioning

confidence: 99%

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Petrogenesis of layered gabbros and ultramafic rocks from Val Sesia, the Ivrea Zone, NW Italy: trace element and isotope geochemistry

Pin¹,

Sills

1986

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Summary Layered gabbros and ultramafics, well exposed in Val Sesia, have been interpreted as a layered complex. The lower part (LLG; up to 1 km thick) comprises well layered pyroxenites and gabbros with minor peridotite and harzburgite. The upper part consists of fairly homogeneous gabbros (MG), which grade into diorite (up to 5.5 km thick). This gabbro body intrudes already highly deformed metapelites, but is itself relatively undeformed. These two groups (LLG and MG-diorite) are distinct on the basis of isotope, trace element and major element chemistry and cannot have been derived from the same liquid. The LLG has ɛ Nd ranging from +1.5 to +2.5 and ɛ Sr from +7 to −8 and was derived from a depleted source. The MG-diorite body has ɛ Sr ranging from +40 to +60 and a wide range of ɛ Nd from −2 to −6. The LLG pyroxenites and gabbros are dominantly cumulates of clinopyroxene with lesser amounts of orthopyroxene. Cumulus plagioclase appears towards the top of the LLG. The LLG is strongly depleted in LREE and LIL elements and was derived from a basaltic liquid with relatively depleted trace element characteristics. It probably fractionated at moderate pressures and was emplaced into the Ivrea Zone along with the adjacent Balmuccia peridotite. The MG comprises plagioclase ± olivine cumulates with minor cumulus apatite, ilmenite and pyroxene. The diorites additionally contain cumulus biotite. The whole body has strongly LREE-enriched patterns (Ce N 4.5–20) and large positive Eu anomalies (Eu/Eu* from 2–12). The MG has calc-alkaline features with high Ba and low Nb. The parental magma was also LREE-enriched, with low Ni, Cr and MgO and high Ba. It was possibly an andesite. The spread in ɛ Nd cannot be accounted for by contamination by any of the likely crustal contaminants. The spread in intial isotope ratios either results from a heterogeneous enriched mantle source or from a two stage process involving remelting of an intermediate mafic reservoir with moderate enrichment in Rb and LREE. The MG-diorite body was emplaced into sediments already undergoing amphibolite-facies metamorphism at pressures of 5–7 kbar. It appears as if the development of magma chambers in the crust was an important process of crustal growth in the Ivrea Zone.

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Section: Isotopic Compositionmentioning

confidence: 78%

Section: Lower Layered Group (Llg) Petrography and Mineral Chemistrymentioning

confidence: 99%

“…(4) A prominent layer, 50-100 m thick, of granulite-facies metasediment which separates the LLG and MLG from more homogeneous gabbros (Ferrario et al 1982). …”

Section: Geological Settingmentioning

confidence: 99%

Section: Lower Layered Group (Llg) Petrography and Mineral Chemistrymentioning

confidence: 99%

Section: Composition Of Parental Liquidmentioning

confidence: 99%

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