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Isotopic investigations of granulites from northwest Scotland and west NorwayCohen, Anthony Stephen January 1988 (has links)
No description available.
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Origin of rutile-bearing ilmenite Fe-Ti deposits in Proterozoic anorthosite massifs of the Grenville ProvinceMorisset, Caroline-Emmanuelle 11 1900 (has links)
The Saint-Urbain and Big Island rutile-bearing ilmenite Fe-Ti oxide deposits are located
in the composite 450 km² Saint-Urbain anorthosite (1055-1046 Ma, U-Pb zircon) and in
the Lac Allard intrusion (1057-1062 Ma, U-Pb zircon) of the 11,000 km² Havre-Saint
Pierre anorthosite suite, respectively, in the Grenville Province of Eastern Canada. Slow
cooling rates of 3-4°C/m.y. are estimated for both anorthosites, based on combined U-Pb
zircon/rutile/apatite and ⁴⁰Ar/³⁹ Ar biotite/plagioclase geochronology, and resulted from
emplacement during the active Ottawan Orogeny. Slow cooling facilitated (1) diffusion
of Zr from ilmenite and rutile, producing thin (10-100 microns) zircon rims on these
minerals, and (2) formation of sapphirine via sub-so lidus reactions of the type: spinel +
orthopyroxene + rutile ± corundum → sapphirine + ilmenite. New chemical and
analytical methods were developed to determine the trace element concentrations and Hf
isotopic compositions of Ti-based oxides. Rutile is a magmatic phase in the deposits
with minimum crystallization temperatures of 781°C to 1016°C, calculated by Zr-in
rutile thermometry. Ilmenite present in rutile-free samples has higher Xhem (hematite
proportion in ilmenite), higher high field strength element concentrations (Xhem = 30-17;
Nb = 16.1-30.5 ppm; Ta 1.28-1.70 ppm), and crystallized at higher temperatures than
ilmenite with more fractionated compositions (Xhem = 21-11; Nb = 1.36-3.11 ppm; Ta =
<0.18 ppm) from rutile-bearing rocks. The oxide deposits formed by density segregation
and accumulation at the bottom of magma reservoirs, in conditions closed to oxygen,
from magmas enriched in Fe and Ti. The initial ¹⁷⁶Hf/¹⁷⁷ Hf of rutile and ilmenite (Saint
Urbain [SU] = 0.28219-0.28227, Big Island [BI] = 0.28218-0.28222), and the initial Pb
isotopic ratios (e.g.²⁰⁶Pb/²⁰⁴ Pb: SU = 17.134-17.164, BI = 17.012-17.036) and ⁸⁷Sr/⁸⁶ Sr
(SU = 0.70399-0.70532, BI = 0.70412-0.70427) of plagioclase from the deposits overlap
with the initial isotopic ratios of ilmenite and plagioclase from each host anorthosite,
which indicates that they have common parent magmas and sources. The parent magmas
were derived from a relatively depleted mantle reservoir that appears to be the primary
source of all Grenvillian anorthosite massifs and existed for --600 m.y. along the margin
of Laurentia during the Proterozoic.
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Origin of rutile-bearing ilmenite Fe-Ti deposits in Proterozoic anorthosite massifs of the Grenville ProvinceMorisset, Caroline-Emmanuelle 11 1900 (has links)
The Saint-Urbain and Big Island rutile-bearing ilmenite Fe-Ti oxide deposits are located
in the composite 450 km² Saint-Urbain anorthosite (1055-1046 Ma, U-Pb zircon) and in
the Lac Allard intrusion (1057-1062 Ma, U-Pb zircon) of the 11,000 km² Havre-Saint
Pierre anorthosite suite, respectively, in the Grenville Province of Eastern Canada. Slow
cooling rates of 3-4°C/m.y. are estimated for both anorthosites, based on combined U-Pb
zircon/rutile/apatite and ⁴⁰Ar/³⁹ Ar biotite/plagioclase geochronology, and resulted from
emplacement during the active Ottawan Orogeny. Slow cooling facilitated (1) diffusion
of Zr from ilmenite and rutile, producing thin (10-100 microns) zircon rims on these
minerals, and (2) formation of sapphirine via sub-so lidus reactions of the type: spinel +
orthopyroxene + rutile ± corundum → sapphirine + ilmenite. New chemical and
analytical methods were developed to determine the trace element concentrations and Hf
isotopic compositions of Ti-based oxides. Rutile is a magmatic phase in the deposits
with minimum crystallization temperatures of 781°C to 1016°C, calculated by Zr-in
rutile thermometry. Ilmenite present in rutile-free samples has higher Xhem (hematite
proportion in ilmenite), higher high field strength element concentrations (Xhem = 30-17;
Nb = 16.1-30.5 ppm; Ta 1.28-1.70 ppm), and crystallized at higher temperatures than
ilmenite with more fractionated compositions (Xhem = 21-11; Nb = 1.36-3.11 ppm; Ta =
<0.18 ppm) from rutile-bearing rocks. The oxide deposits formed by density segregation
and accumulation at the bottom of magma reservoirs, in conditions closed to oxygen,
from magmas enriched in Fe and Ti. The initial ¹⁷⁶Hf/¹⁷⁷ Hf of rutile and ilmenite (Saint
Urbain [SU] = 0.28219-0.28227, Big Island [BI] = 0.28218-0.28222), and the initial Pb
isotopic ratios (e.g.²⁰⁶Pb/²⁰⁴ Pb: SU = 17.134-17.164, BI = 17.012-17.036) and ⁸⁷Sr/⁸⁶ Sr
(SU = 0.70399-0.70532, BI = 0.70412-0.70427) of plagioclase from the deposits overlap
with the initial isotopic ratios of ilmenite and plagioclase from each host anorthosite,
which indicates that they have common parent magmas and sources. The parent magmas
were derived from a relatively depleted mantle reservoir that appears to be the primary
source of all Grenvillian anorthosite massifs and existed for --600 m.y. along the margin
of Laurentia during the Proterozoic.
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Origin of rutile-bearing ilmenite Fe-Ti deposits in Proterozoic anorthosite massifs of the Grenville ProvinceMorisset, Caroline-Emmanuelle 11 1900 (has links)
The Saint-Urbain and Big Island rutile-bearing ilmenite Fe-Ti oxide deposits are located
in the composite 450 km² Saint-Urbain anorthosite (1055-1046 Ma, U-Pb zircon) and in
the Lac Allard intrusion (1057-1062 Ma, U-Pb zircon) of the 11,000 km² Havre-Saint
Pierre anorthosite suite, respectively, in the Grenville Province of Eastern Canada. Slow
cooling rates of 3-4°C/m.y. are estimated for both anorthosites, based on combined U-Pb
zircon/rutile/apatite and ⁴⁰Ar/³⁹ Ar biotite/plagioclase geochronology, and resulted from
emplacement during the active Ottawan Orogeny. Slow cooling facilitated (1) diffusion
of Zr from ilmenite and rutile, producing thin (10-100 microns) zircon rims on these
minerals, and (2) formation of sapphirine via sub-so lidus reactions of the type: spinel +
orthopyroxene + rutile ± corundum → sapphirine + ilmenite. New chemical and
analytical methods were developed to determine the trace element concentrations and Hf
isotopic compositions of Ti-based oxides. Rutile is a magmatic phase in the deposits
with minimum crystallization temperatures of 781°C to 1016°C, calculated by Zr-in
rutile thermometry. Ilmenite present in rutile-free samples has higher Xhem (hematite
proportion in ilmenite), higher high field strength element concentrations (Xhem = 30-17;
Nb = 16.1-30.5 ppm; Ta 1.28-1.70 ppm), and crystallized at higher temperatures than
ilmenite with more fractionated compositions (Xhem = 21-11; Nb = 1.36-3.11 ppm; Ta =
<0.18 ppm) from rutile-bearing rocks. The oxide deposits formed by density segregation
and accumulation at the bottom of magma reservoirs, in conditions closed to oxygen,
from magmas enriched in Fe and Ti. The initial ¹⁷⁶Hf/¹⁷⁷ Hf of rutile and ilmenite (Saint
Urbain [SU] = 0.28219-0.28227, Big Island [BI] = 0.28218-0.28222), and the initial Pb
isotopic ratios (e.g.²⁰⁶Pb/²⁰⁴ Pb: SU = 17.134-17.164, BI = 17.012-17.036) and ⁸⁷Sr/⁸⁶ Sr
(SU = 0.70399-0.70532, BI = 0.70412-0.70427) of plagioclase from the deposits overlap
with the initial isotopic ratios of ilmenite and plagioclase from each host anorthosite,
which indicates that they have common parent magmas and sources. The parent magmas
were derived from a relatively depleted mantle reservoir that appears to be the primary
source of all Grenvillian anorthosite massifs and existed for --600 m.y. along the margin
of Laurentia during the Proterozoic. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
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Geochemical and Petrographic Characterization of the Transition Boundary between the MG2 package to MG3 package at Dwarsrivier Chrome Mine, Bushveld Complex, South AfricaRamushu, Adam Puleng January 2018 (has links)
Magister Scientiae - MSc (Earth Science) / This study area is situated within the Eastern Bushveld complex at Dwarsrivier chrome mine, which is approximately 30 km from Steelpoort and 60km from Lydenburg in the Mpumalanga province. The primary aim of the project is to identify the petrological and geochemical characteristics that can be used to distinguish the various rock types of feldspathic pyroxenites, chromitites, anorthosites and chromitite pyroxenites and determine whether the various rock types are from the MG2 package and MG3 package were formed from a single or multiple magma pulses. The geochemical and mineralogical variation studies were carried out using cores from borehole DWR74 and DWR172 located on the farm Dwarsrivier 372 KT. Using the combination of various multivariate statistical techniques (factor, cluster and discriminant analysis) multi element diagrams and trace element ratios, the outcome of the study demonstrated that each of the four rock types can be sub-divided into two groups.
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