scholarly journals The Kræmer Ø syenite, Kangerdlugssuaq: preliminary description of one of the voluminous oversaturated syenites of the East Greenland Tertiary

1991 ◽  
Vol 38 ◽  
pp. 145-151
Author(s):  
C. K. Brooks
Keyword(s):  
Main Part ◽  
Basaltic Magma ◽  
Coarse Grained ◽  
Skaergaard Intrusion ◽  
East Greenland ◽  
Partial Melt ◽  
Basaltic Melt ◽  
Basaltic Magmas ◽  
Modal Layering ◽  
Preliminary Description

Tue Kræmer Ø syenite, situated close to the Skaergaard intrusion, is typical of many oversturated syenites in the area. It consists of a maginal breccia with a sharp contact to the surrounding gneisses. This breccia, about 150 m wide is made up of basaltic clasts in a granitic matrix. It is associated with pegmatites, aplites and granophyres, all with a non-peralkaline characters. Tue main part of the syenite is a coarse-grained, massively jointed body with many large basic xenoliths and occasional modal layering. It is associated with peralkaline rhyolitic dikes and pegmatites. Anatexis of basement and crystal differentiation from a basaltic magma are thought to be unlikely processes to explain the origin of the syenites although the breccia matrix appears to be a simple partial melt of the gneisses. It is postulated thai such an anatectic melt, formed by heat transfer from basaltic magmas, becomes modified by diffusive interchange with the basaltic melt to generate the syenite in the way described for a nearby locality by Nielsen & Brooks (1988).

scholarly journals In situ fractionation and inward migration of the solidification front in the Skaergaard intrusion, East Greenland

1969 ◽  
Vol 35 ◽  
pp. 59-62
Author(s):  
Troels F.D. Nielsen
Keyword(s):  
Grain Size ◽  
Solidification Front ◽  
Genetic Model ◽  
Basaltic Magma ◽  
Systematic Sampling ◽  
Skaergaard Intrusion ◽  
East Greenland ◽  
The Earth ◽  
Natural Laboratory

For more than 80 years the Skaergaard intrusion, 68°N in southern East Greenland, has been a foremost natural laboratory for the study of the crystallisation and fractionation of basaltic magma. This process has been of prime importance in the evolution of the Earth and other stony planets. Models that have been developed and refined during numerous studies of this particular intrusion have been part of the foundation for petrogenetic modelling for decades. In later years, vast amounts of new data have been added, due to systematic sampling in the field and from analysis of exploration drill cores. Methods for the study on grain-size scale have advanced, and the quest for a wellsupported genetic model for the PGE-Au mineralisation of the intrusion has intensified. The new data and insight question the applicability of conventional petrogenetic modelling, and as a consequence, increasing importance is placed on in situ crystallisation and fractionation in mush zones at the roof, walls and floor of the intrusion.

The East Greenland continental margin, the Prinsen af Wales Bjerge and new Skaergaard intrusion initiatives

2001 ◽  
pp. 83-98
Author(s):  
Troels F.D. Nielsen ◽  
Henriette Hansen ◽  
C. Kent Brooks ◽  
Charles E. Lesher
Keyword(s):  
Continental Margin ◽  
Mineral Exploration ◽  
Science Research ◽  
Field Work ◽  
Alkaline Magmatism ◽  
Skaergaard Intrusion ◽  
East Greenland ◽  
Geological Processes ◽  
Break Up ◽  
Petroleum Company

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Nielsen, T. F., Hansen, H., Brooks, C. K., & Lesher, C. E. (2001). The East Greenland continental margin, the Prinsen af Wales Bjerge and new Skaergaard intrusion initiatives. Geology of Greenland Survey Bulletin, 189, 83-98. https://doi.org/10.34194/ggub.v189.5162 _______________ The rifted volcanic margin of East Greenland has remained a major area for field studies and the development of models for the dynamics of plume-related continental break-up since the start of the Danish Lithosphere Centre (DLC) in 1994. The studies cover a range of disciplines and geological processes from the early development of pre-break-up basin formation and sedimentation over the main phase of basaltic magmatism to the late stages of alkaline magmatism and structural re-equilibration. The East Greenland field activities in the summer of 2000, collectively referred to as EG 2000, were facilitated by a logistic platform provided by support from Statens Naturvidenskabelige Forskningsråd (SNF, the Danish Natural Science Research Council) and the Bureau of Minerals and Petroleum (BMP) in Nuuk, Greenland for the retrieval of 6 km of drillcore from the Skaergaard intrusion. During 1989 and 1990 mineral exploration had resulted in drilling of more than 15 km of core through the classic layered gabbros. The logistic platform also provided support for DLC and Geological Survey of Denmark and Greenland (GEUS) field work and projects throughout the Kangerlussuaq region and on the Blosseville Kyst (Fig. 1), as well as mineral exploration and petroleum company activities.

scholarly journals The perigranitic W-Au Salau deposit (Pyrenees, France): polyphase genesis of a late Variscan intrusion related deposit

2021 ◽  
Vol 192 ◽  
pp. 22
Author(s):  
Thomas Poitrenaud ◽  
Éric Marcoux ◽  
Romain Augier ◽  
Marc Poujol
Keyword(s):  
3D Modeling ◽  
Main Part ◽  
Isotopic Analysis ◽  
Shear Zones ◽  
Coarse Grained ◽  
Axial Zone ◽  
The Past ◽  
Regional Deformation ◽  
Deposit Type ◽  
Ore Types

A field study combined with a laboratory study and 3D modeling have been performed in order to decipher the genesis of the Salau deposit W-Au mineralization (Pyrenees, France), one of the most important for tungsten in Europe. Results show the existence of two superimposed ore types, emplaced ca. 10 km depth and within decreasing temperature conditions: a calcic silicates skarn with rare scheelite and disseminated sulphides followed by a mineralized breccia with massive sulphides (pyrrhotite and chalcopyrite dominant), coarse-grained scheelite and gold, representing the main part of the ore mined in the past. This breccia is localized in ductile-brittle shear-zones which crosscut the granodiorite. U/Pb dating on zircon, apatite and scheelite, previously realized, confirmed this polyphase evolution. These two types of mineralization, linked to the emplacement of two successive intrusions as confirmed by sulphur isotopic analysis, granodioritic then leucogranitic, can be classified as belonging to the Intrusion-Related Gold Deposit type (IRGD). The emplacement of the high-grade gold and scheelite breccia was initiated by the progressive localization of the regional deformation in the Axial Zone of the Pyrenees during the Permian within E-W dextral-reverse faults.

scholarly journals Lateral Reactive Infiltration in a Vertical Gabbroic Crystal Mush, Skaergaard Intrusion, East Greenland

2013 ◽  
Vol 54 (5) ◽  
pp. 985-1016 ◽  
Author(s):  
Olivier Namur ◽  
Madeleine C. S. Humphreys ◽  
Marian B. Holness
Keyword(s):  
Crystal Mush ◽  
Skaergaard Intrusion ◽  
East Greenland ◽  
Reactive Infiltration

scholarly journals Hydrated Peridotite–Basaltic Melt Interaction Part II: Fast Assimilation of Serpentinized Mantle by Basaltic Magma

2020 ◽  
Vol 8 ◽  
Author(s):  
Anastassia Y. Borisova ◽  
Nail R. Zagrtdenov ◽  
Michael J. Toplis ◽  
Georges Ceuleneer ◽  
Oleg G. Safonov ◽  
...  
Keyword(s):  
Basaltic Magma ◽  
Basaltic Melt

Kinetics of pyrope megacryst reactions in ascending basaltic magma – relevance to high-pressure magmatic crystallization at Elie Ness, East Fife

1984 ◽  
Vol 121 (6) ◽  
pp. 615-620 ◽  
Author(s):  
Colin H. Donaldson
Keyword(s):  
High Pressure ◽  
Phase Equilibria ◽  
Crystallization Temperature ◽  
Basaltic Magma ◽  
Basaltic Melt ◽  
The Stability ◽  
Kinetics Of

AbstractThe rates of resorption of pyrope in basaltic melt and of pyrope decomposition to pyroxene + melt at pressures below the stability of garnet are used to examine the proposition (Chapman, 1976) that pyrope megacrysts in the Elie Ness neck began ascent from the mantle at 1300–1450°C. Both reactions are extremely rapid at these temperatures and yet the petrographic evidence is that neither occurred. Either the transporting magma cooled extremely rapidly during ascent (> 30000 °/h) or, more likely, was considerably cooler than previously proposed. Water was a significant constituent of the magma, and a crystallization temperature for the garnet of as little as 1000 °C is possible, based on existing phase–equilibria data.

Skaergaardite, PdCu, a new platinum-group intermetallic mineral from the Skaergaard intrusion, Greenland

2004 ◽  
Vol 68 (4) ◽  
pp. 615-632 ◽  
Author(s):  
N. S. Rudashevsky ◽  
A. M. McDonald ◽  
L. J. Cabri ◽  
T. F. D. Nielsen ◽  
C. J. Stanley ◽  
...  
Keyword(s):  
New Mineral ◽  
Indentation Hardness ◽  
Skaergaard Intrusion ◽  
East Greenland ◽  
X Ray ◽  
Cscl Type ◽  
Black Streak ◽  
Cscl Structure ◽  
Cubic Structure ◽  
Micro Indentation

AbstractSkaergaardite, PdCu, is a new mineral discovered in the Skaergaard intrusion, Kangerdlugssuaq area, East Greenland. It occurs in a tholeitiic gabbro associated with plagioclase, clinopyroxene, orthopyroxene, ilmenite, titanian magnetite, fayalite and accessory chlorite-group minerals, ferrosaponite, a member of the annite–phlogopite series, hornblende, actinolite, epidote, calcite, ankerite, apatite and baddeleyite. The mineral is found in composite microglobules composed of bornite, chalcocite, digenite, chalcopyrite, with rare cobalt pentlandite, cobaltoan pentlandite, sphalerite, keithconnite, vasilite, zvyagintsevite, (Cu,Pd,Au) and Pt-Fe-Cu-Pd alloys, unnamed PdCu3, (Pd,Cu,Sn), Au3Cu and PdAuCu. Skaergaardite occurs as droplets, equant grains with rounded outlines, subhedral to euhedral crystals and as irregular grains that vary in size from 2 to 75 μm, averaging 22 μm. It is steel grey with a bronze tint, has a black streak, a metallic lustre and is sectile. Neither cleavage nor fracture was observed. The mineral has a micro-indentation hardness of VHN25 = 257. It is isotropic, non-pleochroic and exhibits neither discernible internal reflections nor evidence of twinning. Skaergaardite varies from bright creamy white (associated with bornite and chalcopyrite) to bright white (associated with digenite and chalcocite). Reflectance values in air (and in oil) are: 58.65 (47.4) at 470 nm, 62.6 (51.1) at 546 nm, 64.1 (52.8) at 589 nm and 65.25 (53.95) at 650 nm. The average of 311 electron-microprobe analyses gives: Pd 58.94, Pt 1.12, Au 2.23, Cu 29.84, Fe 3.85, Zn 1.46, Sn 1.08, Te 0.28 and Pb 0.39, total 99.19 wt.%, corresponding to (Pd0.967Au0.020Pt0.010)Σ0.997(Cu0.820Fe0.120 Zn0.039Sn0.016Te0.004Pb0.003)Σ1.002. The mineral is cubic, space group Pm3m, a = 3.0014(2) Å, V = 27.0378 Å3, Z = 1. Dcalc is 10.64 g/cm3. The six strongest lines in the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 2.122(100)(110), 1.5000(20)(200), 1.2254(50)(211), 0.9491(20)(310), 0.8666(10)(222), 0.8021(70)(321). The mineral has the CsCl-type structure. It is believed to be isostructural with wairauite (CoFe), synthetic CuZn (β-brass) and is structurally related to hongshiite (PtCu). Skaergaardite developed from a disordered Pd-Cu-rich metal alloy melt that had exsolved from an earlier Cu-(Fe) sulphide melt. Ordering of Pd and Cu (beginning at T ≈ 600°C) results in development of the CsCl structure from a disordered face-centred cubic structure.

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