Solubility of niobium in the system CaCO3?CaF2?NaNbO3 at 0.1�GPa pressure: implications for the crystallization of pyrochlore from carbonatite magma

2004 ◽  
Vol 148 (3) ◽  
pp. 281-287 ◽  
Author(s):  
Roger H. Mitchell ◽  
Bruce A. Kjarsgaard
Keyword(s):  
Carbonatite Magma

Forsterite reprecipitation and carbon dioxide entrapment in the lithospheric mantle during its interaction with carbonatitic melt: a case study from the Sung Valley ultramafic–alkaline–carbonatite complex, Meghalaya, NE India

2020 ◽  
pp. 1-12
Author(s):  
Shubham Choudhary ◽  
Koushik Sen ◽  
Santosh Kumar ◽  
Shruti Rana ◽  
Swakangkha Ghosh
Keyword(s):  
Carbon Dioxide ◽  
Lithospheric Mantle ◽  
Experimental Studies ◽  
Carbonatite Complex ◽  
Kerguelen Plume ◽  
Ne India ◽  
Isotopic Analyses ◽  
Oxygen Isotopic ◽  
Carbonatite Magma

Abstract Carbonatite melts derived from the mantle are enriched in CO2- and H2O-bearing fluids. This melt can metasomatize the peridotitic lithosphere and liberate a considerable amount of CO2. Experimental studies have also shown that a CO2–H2O-rich fluid can form Fe- and Mg-rich carbonate by reacting with olivine. The Sung Valley carbonatite of NE India is related to the Kerguelen plume and is characterized by rare occurrences of olivine. Our study shows that this olivine is resorbed forsterite of xenocrystic nature. This olivine bears inclusions of Fe-rich magnesite. Accessory apatite in the host carbonatite contains CO2–H2O fluid inclusions. Carbon and oxygen isotopic analyses indicate that the carbonatites are primary igneous carbonatites and are devoid of any alteration or fractionation. We envisage that the forsterite is a part of the lithospheric mantle that was reprecipitated in a carbonatite reservoir through dissolution–precipitation. Carbonation of this forsterite, during interaction between the lithospheric mantle and carbonatite melt, formed Fe-rich magnesite. CO2–H2O-rich fluid derived from the carbonatite magma and detected within accessory apatite caused this carbonation. Our study suggests that a significant amount of CO2 degassed from the mantle by carbonatitic magma can become entrapped in the lithosphere by forming Fe- and Mg-rich carbonates.

scholarly journals The Case for Primary, Mantle-derived Carbonatite Magma

1998 ◽  
Vol 39 (11-12) ◽  
pp. 1895-1903 ◽  
Author(s):  
R. E. Harmer ◽  
J. Gittins
Keyword(s):  
Carbonatite Magma

Carbonatite lapilli-bearing tuff and a dolomite carbonatite bomb from Murumuli crater, Katwe volcanic field, Uganda

2000 ◽  
Vol 64 (4) ◽  
pp. 641-650 ◽  
Author(s):  
F. Stoppa ◽  
A. R. Woolley ◽  
F. E. Lloyd ◽  
N. Eby
Keyword(s):  
Volcanic Field ◽  
Chemical Analyses ◽  
Molten State ◽  
Mantle Origin ◽  
State Chemical ◽  
Carbonatite Magma

AbstractA group of carbonate-rich tuffs are described from the Murumuli crater, Katwe-Kikorongo volcanic field, SW Uganda which contain abundant carbonatite pelletal lapilli, together with melilitite lapilli and a range of xenocrysts and lithic fragments including clinopyroxenites considered to be of mantle origin. The carbonatite lapilli consist essentially of Sr-bearing calcite and Mg-calcite which form quench-textured laths. The lapilli contain microphenocrysts of Ti-magnetite, perovskite, apatite, clinopyroxene, sanidine and altered prisms of melilite. A 7 cm long dolomite carbonatite bomb is described which displays a form typically assumed by lava clots erupted in a molten state. Chemical analyses of a tuff, the bomb and a range of minerals are presented. Carbonatite clearly played an important role in the Katwe-Kikorongo magmatism and it is suggested that carbonatite magma evolved from carbonate-bearing melilitite.

scholarly journals Fluid release in carbonatitic systems and its implication for carbonatite magma ascent, compositional evolution and REE-mineralization

2021 ◽  
Author(s):  
Benjamin Walter ◽  
R. Johannes Giebel ◽  
Matthew Steele-MacInnis ◽  
Michael A.W. Marks ◽  
Jochen Kolb ◽  
...  
Keyword(s):  
Magma Ascent ◽  
Compositional Evolution ◽  
Ree Mineralization ◽  
Fluid Release ◽  
Carbonatite Magma

Phlogopitization of pyroxenite; its bearing on the composition of carbonatite magmas

1975 ◽  
Vol 112 (5) ◽  
pp. 503-507 ◽  
Author(s):  
J. Gittins ◽  
C. R. Allen ◽  
A. F. Cooper
Keyword(s):  
Evolutionary History ◽  
Ultramafic Rock ◽  
Aqueous Fluid ◽  
Typical Development ◽  
Experimental Phase ◽  
Carbonatite Complex ◽  
History Of ◽  
The Common ◽  
Alumina Activity ◽  
Carbonatite Magma

SummaryPhlogopitization of pyroxenite is common in contact zones between clinopyroxenites and carbonatite dikes of the Cargill ultramafic rock—carbonatite complex near Kapuskasing, Ontario. The most typical development is a mica zone 1–10 cm wide but phlogopite is also developed in a more pervasive manner throughout the groundmass of several types of ultramafic rock. Fenitization is most commonly thought of as a process whereby aegirine and riebeckitic amphiboles are formed in the host rock while feldspar is recrystallized and silica progressively removed. Phlogopitization of pyroxenite can properly be referred to, however, as a type of fenitization. It is clearly related to the intrusion of carbonatite into pyroxenite and is further testimony to the fact that many carbonatite magmas are initially alkalic but lose alkalies to the surrounding rocks and crystallize as calcitic and dolomitic carbonatite with alkali contents restricted to the amounts that could be fixed as micas, pyroxenes or amphiboles. This in turn is controlled by the silica and alumina activity of the carbonatite magma. Abundant evidence for considerable amounts of fluorine in carbonatite magmas suggests that alkalies may be transported into the country rocks as fluorides. It is further suggested that late-stage feldspathization in carbonatite complexes is explained by the abstraction of potassic halide solutions from the crystallizing carbonatite magma. The conclusion seems inescapable that alkali carbonatite magmas, far from being the curiosity thought by many petrologists, are in fact very common during the evolutionary history of carbonatites. The common calcitic and dolomitic carbonatites have not generally crystallized from a magma of the same composition but are the residue remaining after the abstraction of an alkali-rich aqueous fluid. Consequently, there is a need to redesign the experimental phase equilibrium approach to problems of carbonatite genesis in order to take account of the presence of alkalies in most carbonatite magmas.

scholarly journals Protolith Oceanic Island Arc dari Granitoid Tipe M dan I di Karangsambung, Kebumen, Jawa Tengah

2019 ◽  
Vol 20 (4) ◽  
pp. 249
Author(s):  
Chusni Ansori ◽  
Shaban Godang ◽  
Defry Hastria ◽  
Isyqi Isyqi
Keyword(s):  
Field Studies ◽  
Oceanic Island ◽  
Island Arc ◽  
Rock Fragments ◽  
Geochemical Study ◽  
Mid Ocean Ridge ◽  
Granitoid Rocks ◽  
Ocean Ridge ◽  
Mantle Magma ◽  
Carbonatite Magma

Granitoid rocks which found at Luk Ulo melange complex as rock fragments with  pale gray colour and faneritic texture. Petrogenesis and geotectonic of the granitoid is under debate. Some geologists consider as plagiogranite, which is formed from the Mid Ocean-ridge (MOR); or leucogranite which is formed from continental collision, and others argue as arc-related granitoid type.The field studies ware carried out on 5 (five) tracks around Luk Ulo River and 1 (one) track at Lokidang River. The pale grey Karangsambung granitoid is composed of the mainly  K-feldspar (34-55%), plagioclase (10-25%) and quartz (25-35%), and chemically contains SiO2 (61.25 - 66.06%); Al2O3 (13.94 – 14.61%), K2O (2.53 - 4.00%), Na2O (3.42 - 4.10%), CaO (2.32 - 4.76%), Fe2O3 total (5.85 – 8.71%), MgO (0.98 – 1.97%). The granitoid is M- and I-type that were formed at 760o - 800o C with a depth of about 20-30 km, resulting from the differentiation of magma from a fragment origin of the K-enriched oceanic island arc originating from drifting of the IAB fragment. The sample of basalt 17D has a relatively high of Nb/Ta ratio (20), low Rb (<2 ppm), low Ba (17 ppm), and is interpreted as interacting with MORB mantle magma containing rutile-melt;whereas quartz monzonite (17A) has a relatively low of Zr/Sm ratio (3.86), which is indicated to have been contaminated by a carbonatite magma. The spidergram pattern of mantle metagabbro (sample no. 13) similar with the basalt from IAB-Bransfield Strait (Antarctica). Results of a comprehensive geochemical study proposes that the current condition of the Karangsambung zone is part of geotectonic of ACM-Eurasia, that composed of a combination of four rock fragments, i.e. (a) the rocks which sourced from IAB fragments, (b) mantle MORB, (c) continental crust from the origin of ACM-Eurasia, (d) the origin fragment from carbonatite magma.Keyword: Luk Ulo Melange Complex, pale grey granitoid, Island-arc granitoid, M  and I-type granitoid

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