Vanadian allanite-(La) and Vanadian allanite-(Ce) from the Hemlo gold deposit, Ontario, Canada

AbstractAllanite-(La) (containing up to 7.80 wt.% V2O3 and with La/ΣREE and La/Ce atomic ratios up to 0.54 and 1.45, respectively) and allanite-(Ce) (up to 8.46 wt.% V2O3) occur in close association with vanadian muscovite, barian tomichite and vanadian titanite in the main ore zone of the Hemlo gold deposit, Ontario, Canada. Allanite-(Ce) generally occurs as a minor constituent in cross-cutting veins or along foliation planes, whereas allanite-(La) invariably occurs in direct contact with titanite. The high V concentrations in the allanites from Hemlo are readily attributable to an adequate local source of this element, and are most likely controlled mainly by a simple substitution of V for Al in octahedral coordination. Vanadian allanite-(La) and vanadian allanite-(Ce), without any systematic differences in other constituents, are clearly distinct in REE composition, in respect to both the relative concentrations of La and Ce and abundances of other REE. The formation of both allanites (Ce- and La-rich) indicates very localised remobilisation and concentration of REE during a late hydrothermal alteration. The unusual REE composition of vanadian allanite-(La) directly reflects partitioning of REE with coexisting titanite, and the formation of this unusual phase may be attributable to replacement of earlier titanite with redistribution of REE in the solid state.

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The Yatela gold deposit in Mali, West Africa: The final product of a long-lived history of hydrothermal alteration and weathering

Journal of African Earth Sciences ◽

10.1016/j.jafrearsci.2015.10.006 ◽

2016 ◽

Vol 113 ◽

pp. 73-87 ◽

Cited By ~ 9

Author(s):

Quentin Masurel ◽

John Miller ◽

Kim A.A. Hein ◽

Eric Hanssen ◽

Nicolas Thébaud ◽

...

Keyword(s):

West Africa ◽

Gold Deposit ◽

Hydrothermal Alteration ◽

History Of

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Environmental control on the variability of DMS and DMSP in the Mauritanian upwelling region

Biogeosciences ◽

10.5194/bg-9-1041-2012 ◽

2012 ◽

Vol 9 (3) ◽

pp. 1041-1051 ◽

Cited By ~ 22

Author(s):

C. Zindler ◽

I. Peeken ◽

C. A. Marandino ◽

H. W. Bange

Keyword(s):

Surface Waters ◽

Coastal Upwelling ◽

Environmental Control ◽

Hot Spot ◽

Local Source ◽

Surface Seawater ◽

Near Surface ◽

Northwest Africa ◽

N:P Ratios ◽

A Minor

Abstract. Dimethylsulphide (DMS) and dissolved and particulate dimethylsulfoniopropionate (DMSPd, DMSPp) were measured in near-surface waters along the Mauritanian coast, Northwest Africa, during the upwelling season in February 2008. DMS, DMSPd and DMSPp surface concentrations of up to 10 nmol L−1, 15 nmol L−1 and 990 nmol L−1, respectively, were measured. However, the DMS concentrations measured are in the low range compared to other upwelling regions. The maximum DMSPp concentration is the highest reported from upwelling regions so far, which might indicate that the Mauritanian upwelling is a hot spot for DMSP. Within the phytoplankton groups, dinoflagellates were identified as important contributors to DMS concentrations, while other algae seemed to have only a minor or no influence on DMS and DMSP concentrations. A pronounced switch from high DMSP to high DMS concentrations was observed when the nitrogen to phosphorus ratio (N:P) was below 7. The high DMS/DMSP ratios at N:P ratios <7 indicate that nitrogen limitation presumably triggered a switch from DMSP to DMS independent of the species composition. Our results underline the importance of coastal upwelling regions as a local source for surface seawater sulphur.

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Hydrothermal alteration at the Mineral Hill Mine, Jardine, Montana; a lower amphibolite facies Archean lode gold deposit of probable synmetamorphic origin; reply

Economic Geology ◽

10.2113/gsecongeo.92.3.378 ◽

1997 ◽

Vol 92 (3) ◽

pp. 378-379

Author(s):

David S. Smith

Keyword(s):

Gold Deposit ◽

Hydrothermal Alteration ◽

Amphibolite Facies ◽

Lode Gold ◽

Lode Gold Deposit

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Hydrothermal alteration at the Mineral Hill Mine, Jardine, Montana; a lower amphibolite facies Archean lode gold deposit of probable synmetamorphic origin; discussion

Economic Geology ◽

10.2113/gsecongeo.92.3.377 ◽

1997 ◽

Vol 92 (3) ◽

pp. 377-378

Author(s):

Ora H. Rostad

Keyword(s):

Gold Deposit ◽

Hydrothermal Alteration ◽

Amphibolite Facies ◽

Lode Gold ◽

Lode Gold Deposit

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Heterogeneous Formation of Oriented Silicon Oxynitride on α-Si3N4 Seed Crystals : Habits And Radiation Stability

Microscopy and Microanalysis ◽

10.1017/s1431927600017219 ◽

1999 ◽

Vol 5 (S2) ◽

pp. 778-779

Author(s):

R.W Carpenter ◽

W Braue ◽

M.J. Kim

Keyword(s):

Silicon Nitride ◽

Heterogeneous Nucleation ◽

Radiation Stability ◽

Silicon Oxynitride ◽

Minor Constituent ◽

Sintering Aids ◽

Sintering Aid ◽

Nucleation Sites ◽

Heterogeneous Formation ◽

A Minor

Lath-like silicon oxynitride crystals have often been observed in the microstructure of silicon nitride based ceramics after processing. They are usually located in glassy regions which are siliceous solidified sintering aid liquid, and usually contain a small (∼100nm) a-Si3N4 crystal. These nitride crystals are considered to be seeds, incompletely dissolved in the melt, that are heterogeneous nucleation sites for the oxynitride crystals. We present here the first observations of morphological and crystallographic habits between the seed nanocrystals and the host oxynitride laths.Fig. 1 shows a typical oxynitride lath containing a nitride seed crystal. The lath is surrounded by glass and ß-Si3N4 particles, and a small cristobalite particle (a minor constituent). This microstructure is from an Si02-Si3N4 ceramic processed with Al2O3 sintering aid. The same oxynitride lath/seed structures were observed when other sintering aids (eg. Y2O3, MgO, ZrO2) were used, so they are independent of sintering aid.

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Betaine Yields from Marine Algal Species Utilized in the Preparation of Seaweed Extracts Used in Agriculture

Natural Product Communications ◽

10.1177/1934578x1000500418 ◽

2010 ◽

Vol 5 (4) ◽

pp. 1934578X1000500 ◽

Cited By ~ 6

Author(s):

Gerald Blunden ◽

Peter F. Morse ◽

Imre Mathe ◽

Judit Hohmann ◽

Alan T. Critchley ◽

...

Keyword(s):

Marine Algae ◽

Algal Species ◽

First Record ◽

Commercial Production ◽

The Other ◽

Minor Constituent ◽

Laminaria Digitata ◽

Seaweed Extracts ◽

Marine Algal ◽

A Minor

Ascophyllum nodosum, and to a lesser extent, Laminaria digitata, L. hyperborea and Fucus serratus, are marine algal species utilized in the commercial production of seaweed extracts used in agriculture. Betaines have been shown to be important constituents of these extracts, but there appears to have been no study made on whether there are variations in the betaine contents of these species based on either the place or date of collection. Samples of each of the four species were collected from widely separated areas at different times of the year. Also, in the case of A. nodosum, approximately monthly collections were made from one location. The betaines detected in the various collections of the same species showed little variation, although in the case of A. nodosum, glycinebetaine was found as a minor constituent in some samples, but was not detected in others. Trigonelline was found in all the tested samples of the two Laminaria species; this is, to our knowledge, the first record of this betaine in marine algae. With the exception of trigonelline in the Laminaria species, the betaine yields from the various samples of L. digitata, L. hyperborea and F. serratus showed little variation, regardless of either the place or date of collection. The trigonelline contents of the Laminaria species collected at one location (Finavarra, Ireland), in particular of L. hyperborea, was substantially greater than those from the other places of collection. In the case of A. nodosum, the betaine yields from samples collected at one site (Dale, Pembrokeshire, UK) were significantly higher than those from the other places of collection, which were very similar to each other. There was no clear indication of seasonal variation in betaine yields from A. nodosum.

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