scholarly journals Salty kimberlite of the Udachnaya-East pipe (Yakutia, Russia): a petrological oddity, a victim of contamination or a new magma type?

2019 ◽  
Keyword(s):  
Magma Type

Garnet-Pyroxenite-Derived End-Member Magma Type in Kamchatka: Evidence from Composition of Olivine and Olivine-Hosted Melt Inclusions in Holocene Rocks of Kekuknaisky Volcano

Petrology ◽  
2018 ◽  
Vol 26 (4) ◽  
pp. 329-350 ◽  
Author(s):  
N. A. Nekrylov ◽  
D. V. Popov ◽  
P. Yu. Plechov ◽  
V. D. Shcherbakov ◽  
L. V. Danyushevsky ◽  
...  
Keyword(s):  
Melt Inclusions ◽  
Magma Type ◽  
Garnet Pyroxenite

Chemistry of chromian spinel in volcanic rocks as a potential guide to magma chemistry

1992 ◽  
Vol 56 (383) ◽  
pp. 173-184 ◽  
Author(s):  
Shoji Arai
Keyword(s):  
Volcanic Rocks ◽  
Island Arc ◽  
Chromian Spinel ◽  
Oceanic Plateau ◽  
Magma Type ◽  
Original Magma ◽  
Back Arc

AbstractChromian spinel in volcanic rocks is a potential discriminant for magma chemistry. The TiO2 content of spinel, compared at similar Fe3+/(Cr + Al + Fe3+) ratios, can distinguish island arc basalts from intraplate basalts. MORB spinels are low in this ratio and are intermediate for the TiO2 level at comparable Fe3+ ratios. Spinels from back-arc basin basalts, although similar in TiO2/Fe3+ ratio, are more enriched in Fe3+ than the MORB spinels. Spinels in the oceanic plateau basalts are distinctly lower in TiO2 than other intraplate basalt spinels and even slightly lower in TiO2 than the MORB spinels. The data were successfully applied to estimate the kind of the magma from which spinelbearing cumulates, especially dunites, were formed. Original magma chemistry of altered or metamorphosed volcanics in which spinels survive can also be estimated by the chemistry of relict spinel alone. It is possible to estimate the magma type of source volcanics for detrital spinel particles of volcanic derivation.

Relative contribution of crust and mantle to flood basalt magmatism, Mahabaleshwar area, Deccan Traps

1984 ◽  
Vol 310 (1514) ◽  
pp. 627-641 ◽  
Keyword(s):  
Trace Element ◽  
Incompatible Element ◽  
Crustal Contamination ◽  
Flood Basalt ◽  
Oceanic Islands ◽  
Magma Type ◽  
Relative Contribution ◽  
History Of ◽  
Crustal Contribution ◽  
Element Enrichment

The 1200 m section of flat-lying basalts in the Mahabaleshwar area is divided into three formations on the basis of the trace elements Sr, Ba, Rb, Zr and Nb. The lowermost unit, the Poladpur Formation, is characterized by high Ba, Rb, and Zr/Nb, and low Sr. These features are accompanied by high K and Si, high and variable 87 Sr/ 86 Sr initial ratios (0.7043 - 0.7196), and low and variable e N d values (+ 2.6 to -17.4). The formation is interpreted as having developed by contamination of the overlying Ambenali magma-type with ancient granitic crust, with simultaneous fractionation of a gabbroic mineral assemblage. The more basic members of the formation are found towards the base of the succession and are more contaminated than the upper flows. The succeeding Ambenali Formation, characterized by the Ambenali magma type, has low Ba, Rb, Sr and Zr/Nb, and low and rather uniform 87 Sr/ 86 Sr initial ratios (0.7038-0.7043) coupled with high and relatively uniform e N d (+4.7 to +6.4). It is interpreted as being essentially uncontaminated and derived from a mantle source with a history of slight trace-element enrichment relative to m.o.r.b.-source. The uppermost group of flows, the Mahabaleshwar Formation, is, like the Poladpur, enriched in Ba, Rb, K and Si relative to the Ambenali, but has lower Zr/Nb and higher Sr. 87 Sr/ 86 Sr initial ratios (0.7040-0.7056) are slightly higher than in the Ambenali, and e N d lies in the range +7.1 to -3.0. In this formation Sr correlates positively with the other incompatible elements and with 87 Sr/ 86 Sr initial ratios. This is in strong contrast to the relations observed in the Poladpur, and we believe that the behaviour of Sr may be a simple pointer to the distinction between mantle and crustal contributions. Assuming that late-stage crystal fractionation processes can be allowed for, if Sr correlates positively with elements such as K, Rb and Ba then mantle enrichment processes are clearly implied. Conversely, as for example in the Poladpur, if the correlation is negative, crustal contamination is suspected because Sr is unlikely to behave as an incompatible element in most crustal derived melts or fluids because of buffering by residual plagioclase. Furthermore, the relative uniformity of the Mahabaleshwar Formation, the position on the Sr and Nd isotope diagram close to the ‘mantle array’, the fact that in terms of both incompatible element concentrations and isotopes the rocks are similar to tholeiites from oceanic islands such as Hawaii and Kerguelen, are all factors that reinforce the conclusion that these are mantle derived magmas which have suffered insignificant crustal contamination. They are, however, derived from a mantle which is trace-element enriched relative to the Ambenali source. Thus in the succession as a whole the crustal contribution appears to be small. Maximum amounts of contamination in the Poladpur Formation are difficult to determine but the average amount is probably in the region of 6-12 percentage mass. The whole sequence therefore contains a crustal contribution of about 2-3%.

scholarly journals "Very High Alumina Basalt": A Mixture and Not a Magma Type

Science ◽  
1974 ◽  
Vol 183 (4130) ◽  
pp. 1214-1215 ◽  
Author(s):  
E. Dowty ◽  
M. Prinz ◽  
K. Keil
Keyword(s):  
High Alumina ◽  
High Alumina Basalt ◽  
Magma Type ◽  
Very High

Differentiation and source of the Nipissing Diabase intrusions, Ontario, Canada

1993 ◽  
Vol 30 (6) ◽  
pp. 1123-1140 ◽  
Author(s):  
P. C. Lightfoot ◽  
H. de Souza ◽  
W. Doherty
Keyword(s):  
Trace Element ◽  
Crustal Contamination ◽  
Primitive Mantle ◽  
Magma Source ◽  
Magma Type ◽  
Ni Content ◽  
Chemical Signatures ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

Major and trace element data are presented for 2.2 Ga Proterozoic diabase sills from across the Nipissing magmatic province of Ontario. In situ differentiation of the magma coupled with assimilation of Huronian Supergroup roof sediments is responsible for the variation in composition between quartz diabase and granophyric diabase seen within many of the differentiated intrusions. Uniform trace element and isotope ratio signatures, such as La/Sm (2.8 – 3.7) and εNdCHUR (−2.7 to −5.9) characterize chilled margins and undifferentiated quartz diabases. These chemical signatures suggest the existence of a single magma source that was parental to intrusions throughout the magmatic province; this magma has higher La/Sm and lower Ti/Y than primitive mantle and is displaced towards the composition of shales. Most chilled diabases and quartz diabases have a similar Mg# (0.64 and 0.60) and Ni content (98 and 127 ppm), and it is argued that the magma differentiated at depth and was emplaced as a uniform low-Mg magma. The Wanapitei intrusion and Kukagami Lake sill are an exception in that although the quartz diabase has La/Sm similar to the Nipissing magma type, which suggests that they came from the same source, the Mg# (0.68–0.71) and Ni content (130–141 ppm) are higher, which may suggest that they are either slightly more primitive examples of the normal Nipissing magma or that cumulus hypersthene has been resorbed. The light rare earth element enriched signature of the Nipissing magmas was perhaps introduced from the continental crust as the magma migrated from the mantle to the surface, but a remarkably constant and large amount (>20%) of crustal contamination would be required. An addition of 1 –3% shale to the source of a transitional mid-ocean ridge basalt type magma can broadly reproduce the compositional features of the Nipissing magma type. The source characteristics were perhaps imparted during subduction accompanying the terminal Kenoran orogeny.

scholarly journals New occurrences of undersaturated syenites from the southern Blosseville Coast, East Greenland

1991 ◽  
Vol 38 ◽  
pp. 153-159
Author(s):  
C. K. Brooks
Keyword(s):  
Dyke Swarm ◽  
Extensive Area ◽  
East Greenland ◽  
Magma Type ◽  
Late Generation ◽  
To Come ◽  
New Occurrences

This note reports hitherto undescribed nepheline-sodalite syenites from I. C. Jacobsen Fjord and Ryberg Fjord. Numerous syenite erratics have been encountered at I. C. Jacobsen Fjord. They are believed to come from a single intrusion in the immediate neighbourhood which has not yet been located. They consist Iargely of perthite with nepheline, sodalite, salitic pyroxene, hastingsitic amphibole, sphene and Fe-Ti oxide. They resemble the pulaskites of the Kangerdlugssuaq intrusion. On the side of the Sorgenfri Gletscher at the head of Ryberg Fjord an extensive area of peralkaline syenite has been found. It consists of perthite, nepheline, sodalite, aegirine, arfvedsonite and very Fe-rich biotite. It is cut by tholeiitic dykes of a late generation of the coastal dyke swarm. These syenites bridge a gap between previously known examples and suggest that the magma type was much commoner than thought originally.

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