75 research outputs found
Sulfatreduzierende Bakterien in Schwefel- und Grubenwässern Deutschlands und Österreichs
The bearing of trace element distribution patterns of deep sea basalts for the interpretation of their genesis
Geochemical and petrological studies of lavas, pyroclastica and associated xenoliths from the Christiana Islands, Aegean Sea
Geochemical and petrological investigations of the volcanic islands of
Christiana proved their genetic connection with the calc-alkaline volcanism of the
Santorini group and the submarine Kolombos volcano. The lavas of Christiana
range from andesite to dacite while pumice is of rhyolithic chemistry. Rather
constant K/Rb ratios indicate consanguine magmas.
Increased Ni, Cr and Mg concentrations in several lavas indicate a certain
admixture of peridotite material to the calc-alkaline magmas.
Xenoliths found below an autochthonous pumice layer prove penetration of
granites, phyllites and limestone by the rising magma. The geochemical investigations
support a subduction type origin of the volcanic material of the Christiana
Islands
27. VARIATION IN SINGLE COOLING UNITS AT HOLE 418A, DEEP SEA DRILLING PROJECT: EFFECTS OF ALTERATION AND PHENOCRYST REDISTRIBUTION
Platinum-group element concentrations in mafic and ultramafic lithologies drilled from the Hess Deep.
This paper reports the first concentrations of platinum-group minerals (PGM) and platinum-group elements (PGE), of tens
of parts per billion, to be described from the lower oceanic crust exposed in Hess Deep, if not the first concentrations reported
from modern-day unsubducted lower oceanic crust. The results indicate that detectable PGE concentrations occur in fastspreading
oceanic crust. The PGE-bearing melt extracted from the mantle provides the potential for PGE to be concentrated in
lower oceanic crustal ultramafic rocks, and this study has identified such concentrations in the magmatic plutonic lithologies
from Hess Deep. However, PGE concentrations calculated in 100% of sulfide reveal that sulfides in the residual mantle
harzburgite at Hess Deep are enriched in PGE relative to lower crustal dunite. Therefore, the harzburgites retain some PGE and
remain fertile for the extraction of more PGE during subduction.
Of the high-level gabbros from Site 894 and gabbro, troctolite, dunite, and harzburgite from Site 895, the troctolite from
Holes 895D and 895E was found to have the maximum values of Pt (36 ppb) and Pd (54 ppb), together with a dunite from Hole
895E, which had maximum values of Pt (24 ppb) and Pd (46 ppb). In both lithologies, the greatest values of PGE coincide with
the greatest modal abundance of base-metal sulfide and chrome-spinel. Detectable values of PGE were observed also in gabbro
and harzburgite and the slightly more PGE-enriched gabbros are also those with relatively depleted concentrations of rare earth
elements (REE).
PGM have been located in both dunite and troctolite. In the troctolite, the most common PGM are alloys of precious and
base metals, specifically Pd-Sn-Cu, Cu-Pt-Au, Pt-Fe-Ni-Cu, and Ni-Pt-Fe. One Pd-Bi-Te mineral was observed. These PGM
are associated with chrome-spinel and pentlandite, which is altering to magnetite, millerite, Ni-Fe alloys, and oxides. Cu-bearing
sulfides and native Cu are present. In the dunite, an Ir-Pt alloy and a Pd-Sn alloy occur close together within a Ni-Fe alloy
Variations of heavy metals in sediments of Rio Catarina passing the city of Monterrey/Nuevo Leon, Mexico
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