Field evidence for successive mixing and mingling between the Piolard Diorite and the Saint-Julien-la-Vêtre Monzogranite (Nord–Forez, Massif Central, France)

1988 ◽  
Vol 25 (1) ◽  
pp. 49-59 ◽  
Author(s):  
Bernard Barbarin
Keyword(s):  
Large Volume ◽  
Mafic Magma ◽  
Complex Field ◽  
Massif Central ◽  
Field Evidence ◽  
Exchange Processes ◽  
Magmatic Enclaves

Recent mapping of the Nord–Forez region, Massif Central, France, reveals a variety of complex field relationships along contacts between a large enclave of diorite and its enclosing monzogranite. Field relations, hybrid rocks, and a wide variety of mafic magmatic enclaves can be explained by a succession of processes between coexisting mafic and felsic magmas that either prevent or promote exchanges. The large volume of mafic magma, and consequently the large amount of heat it brought with it, favored exchange processes. Because the distribution of heat varied with both time and place, the nature and intensity of the compositional exchange processes also varied.Most of the features attributed to exchange are related to processes that occurred at the level of emplacement and after the beginning of crystallization of the two magmas. These processes affected both the granitic and dioritic magmas already thoroughly hybridized by nearly similar processes that took place earlier at depth.

scholarly journals Geochemistry of Gold Ores Mined During Celtic Times from the North-Western French Massif Central

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Sandrine Baron ◽  
Călin G. Tămaș ◽  
Marion Rivoal ◽  
Béatrice Cauuet ◽  
Philippe Télouk ◽  
...  
Keyword(s):  
Western Europe ◽  
Gold Mining ◽  
Isotope Geochemistry ◽  
Ore Deposits ◽  
Mining District ◽  
French Massif Central ◽  
Massif Central ◽  
Gold Ores ◽  
The North ◽  
Field Evidence

AbstractThe Celtic culture of Western Europe left magnificent gold objects, such as jewellery and weapons from nobility graves and hoarded coins, as well as field evidence of pre-Roman gold mining and metallurgical workshops that attest to the mining of local ores. This is the case of Central France where many precious metallic ores have been mined throughout the ages from the Prehistoric times onwards. One of the lingering problems in assessing the provenance of gold artefacts and coins is the lack of relevant data on the isotope geochemistry and mineralogy of ore sources. Forty gold ores samples were collected and studied from Limousin (French Massif Central), a very significant gold mining district from the Celtic times. Their Pb isotope compositions clearly show a local dichotomy i.e. two distinct groups of ores, one of Late Proterozoic to Early Paleozoic Pb model age and another associated to Variscan ages and consistent with field relationships, mineralogy and elemental analyses. The use of Cu and Ag isotopes, and their coupling with Pb isotopes, will refine the tracing of future metal provenance studies, but also highlight some metallurgical practices like deliberate metal additions to gold artefact or debasement of gold coins. The newly acquired Pb, Ag, and Cu isotopic data on gold ores improves our understanding of ore deposits geology and provide clarifications on the provenance of Celtic gold from this area and its economic importance.

A limestone landscape from the air: le Causse Méjean, Languedoc, France

Antiquity ◽  
1999 ◽  
Vol 73 (280) ◽  
pp. 411-419 ◽  
Author(s):  
Peter Fowler
Keyword(s):  
Massif Central ◽  
Field Evidence

Reconnaissance on the southern edge of the Massif Central is studying field evidence which deepens appreciation of the present-day upland French landscape as not only ‘sauvage’ but also the product of long-term use.

Ni, Cu, Au, and platinum-group element contents of sulphides associated with intraplate magmatism: a synthesis

1997 ◽  
Vol 34 (4) ◽  
pp. 337-351 ◽  
Author(s):  
Sarah-Jane Barnes ◽  
M. L. Zientek ◽  
M. J. Severson
Keyword(s):  
Large Volume ◽  
Platinum Group Element ◽  
Tectonic Setting ◽  
Mafic Magma ◽  
Group Element ◽  
Sulphide Deposit ◽  
Sulphide Liquid ◽  
Intraplate Magmatism ◽  
Platinum Group ◽  
The Difference

The tectonic setting of intraplate magmas, typically a plume intersecting a rift, is ideal for the development of Ni – Cu – platinum-group element-bearing sulphides. The plume transports metal-rich magmas close to the mantle–crust boundary. The interaction of the rift and plume permits rapid transport of the magma into the crust, thus ensuring that no sulphides are lost from the magma en route to the crust. The rift may contain sediments which could provide the sulphur necessary to bring about sulphide saturation in the magmas. The plume provides large volumes of mafic magma; thus any sulphides that form can collect metals from a large volume of magma and consequently the sulphides will be metal rich. The large volume of magma provides sufficient heat to release large quantities of S from the crust, thus providing sufficient S to form a large sulphide deposit. The composition of the sulphides varies on a number of scales: (i) there is a variation between geographic areas, in which sulphides from the Noril'sk–Talnakh area are the richest in metals and those from the Muskox intrusion are poorest in metals; (ii) there is a variation between textural types of sulphides, in which disseminated sulphides are generally richer in metals than the associated massive and matrix sulphides; and (iii) the massive and matrix sulphides show a much wider range of compositions than the disseminated sulphides, and on the basis of their Ni/Cu ratio the massive and matrix sulphides can be divided into Cu rich and Fe rich. The Cu-rich sulphides are also enriched in Pt, Pd, and Au; in contrast, the Fe-rich sulphides are enriched in Fe, Os, Ir, Ru, and Rh. Nickel concentrations are similar in both. Differences in the composition between the sulphides from different areas may be attributed to a combination of differences in composition of the silicate magma from which the sulphides segregated and differences in the ratio of silicate to sulphide liquid (R factors). The higher metal content of the disseminated sulphides relative to the massive and matrix sulphides may be due to the fact that the disseminated sulphides equilibrated with a larger volume of magma than massive and matrix sulphides. The difference in composition between the Cu- and Fe-rich sulphides may be the result of the fractional crystallization of monosulphide solid solution from a sulphide liquid, with the Cu-rich sulphides representing the liquid and the Fe-rich sulphides representing the cumulate.

scholarly journals Origin of Talc and Fe-Ti-V Mineralization in the Kletno Deposit (the Śnieżnik Massif, SW Poland)

Minerals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 13
Author(s):  
Grzegorz Gil ◽  
Piotr Gunia ◽  
Jaime D. Barnes ◽  
Michał Szymański ◽  
Petras Jokubauskas ◽  
...  
Keyword(s):  
Mafic Magma ◽  
Bulk Rock ◽  
Massif Central ◽  
Δ13c Values ◽  
Oxygen And Carbon Isotope ◽  
Ore Bodies ◽  
Sw Poland ◽  
Fluid Interaction ◽  
Tectonic Slice ◽  
Δ18o And Δ13c

The Kletno deposit in the Śnieżnik Massif (Central Sudetes, SW Poland), mined for Fe, U, Ag, Cu, fluorite, and marble through the ages, developed at the contact of marbles and orthogneiss. Here, we present a new Fe-Ti-V-ore (containing up to 14.07 wt. % Fe, 2.05 wt. % Ti, and 2055 ppm V in bulk rock) and ornamental- to gem-quality talc prospect at the southwest margin of this deposit. This newly documented Fe-Ti-V mineralization is hosted in hornblendites, dolomite veins, and chlorite schists, which, along with talc, envelopes a tectonic slice of serpentinite. Hornblendites are interpreted as metamorphosed ferrogabbros, derived from the same mafic melts as adjacent barren metagabbros. The oxygen and carbon isotope compositions of metabasites and dolomite veins (amphibole δ18O values = 8.8–9.3‰; carbonate δ18O values = 12.8–16.0‰, and δ13C values = −8.3‰ to −7.2‰), in combination with those of the country marbles (carbonate δ18O and δ13C values = 23.2‰ and +0.1‰, respectively), suggest that mineralization-bearing hornblendites formed due to interaction of the mafic magma with CO2 released during the decarbonation of the sediments. The CO2-bearing fluid interaction with gabbros likely caused carbonation of the gabbros and formation of the dolomite veins, whereas talc formed due to Si-rich fluids, possibly derived from a mafic intrusion, interaction with serpentinite, or due to the metasomatism of the serpentinite–gabbro assemblage. Moreover, fluids leaching Fe and Ti from the adjacent sediments can mix with the mafic magma causing enrichment of the magma in Fe and Ti. Consequently, the mineralization-bearing ferrogabbros became even more enriched in Fe and Ti, which can be linked with the formation of Fe-Ti-V ore bodies.

Selected Abstracts of Recent Research in Stuttering

1999 ◽  
Vol 9 (1) ◽  
pp. 5-6
Author(s):  
Carrie Bain ◽  
Nan Bernstein Ratner
Keyword(s):  
Large Volume ◽  
Clinical Relevance

Due to the large volume of fluency-related publications since the last column, we have chosen to highlight those articles of highest potential clinical relevance.

Intraoperative abdominal ultrasonography-guided large volume ethanol injection for hepatocellular carcinoma

2001 ◽  
Vol 120 (5) ◽  
pp. A482-A482
Author(s):  
R MONDRAGONSANCHEZ ◽  
A GARDUOLOPEZ ◽  
H MURRIETA ◽  
M FRIASMENDIVIL ◽  
R ESPEJO ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Large Volume ◽  
Abdominal Ultrasonography ◽  
Ethanol Injection
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