Formation of Iron-Carbon Alloys in Basaltic Magma at Uivfaq, Disko Island: The Role of Carbon in Mafic Magmas

1985 ◽  
Vol 93 (4) ◽  
pp. 475-492 ◽  
Author(s):  
Cyrena Anne Goodrich ◽  
John M. Bird
Keyword(s):  
Basaltic Magma ◽  
Mafic Magmas

scholarly journals Role of syn-eruptive plagioclase disequilibrium crystallization in basaltic magma ascent dynamics

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
G. La Spina ◽  
M. Burton ◽  
M. de’ Michieli Vitturi ◽  
F. Arzilli
Keyword(s):  
Basaltic Magma ◽  
Magma Ascent

Mafic-silicic layered intrusions: the role of basaltic injections on magmatic processes and the evolution of silicic magma chambers

1996 ◽  
Vol 87 (1-2) ◽  
pp. 233-242 ◽  
Author(s):  
R. A. Wiebe
Keyword(s):  
Basaltic Magma ◽  
Mafic Magma ◽  
Silicic Magma ◽  
Granitic Magma ◽  
Magma Chambers ◽  
Mechanical Mixing ◽  
Diffusive Convection ◽  
Type Granite ◽  
Mafic Magmas ◽  
Silicic Magmas

ABSTRACT:Plutonic complexes with interlayered mafic and silicic rocks commonly contain layers (1–50 m thick) with a chilled gabbroic base that grades upwards to dioritic or silicic cumulates. Each chilled base records the infusion of new basaltic magma into the chamber. Some layers preserve a record of double-diffusive convection with hotter, denser mafic magma beneath silicic magma. Processes of hybridisation include mechanical mixing of crystals and selective exchange of H2O, alkalis and isotopes. These effects are convected away from the boundary into the interiors of both magmas. Fractional crystallisation aad replenishment of the mafic magma can also generate intermediate magma layers highly enriched in incompatible elements.Basaltic infusions into silicic magma chambers can significantly affect the thermal and chemical character of resident granitic magmas in shallow level chambers. In one Maine pluton, they converted resident I-type granitic magma into A-type granite and, in another, they produced a low-K (trondhjemitic) magma layer beneath normal granitic magma. If comparable interactions occur at deeper crustal levels, selective thermal, chemical and isotopic exchange should probably be even more effective. Because the mafic magmas crystallise first and relatively rapidly, silicic magmas that rise away from deep composite chambers may show little direct evidence (e.g. enclaves) of their prior involvement with mafic magma.

Constraints on the formation of the Baogutu reduced porphyry copper deposit (West Junggar, NW China): Assessing the role of mafic magmas in mineralization

Lithos ◽  
2019 ◽  
Vol 336-337 ◽  
pp. 112-124
Author(s):  
Chu Wu ◽  
Tao Hong ◽  
Xing-Wang Xu ◽  
Ming-Jian Cao ◽  
Hao Li ◽  
...  
Keyword(s):  
Porphyry Copper ◽  
Copper Deposit ◽  
Porphyry Copper Deposit ◽  
Nw China ◽  
West Junggar ◽  
Mafic Magmas

Chemostratigraphic division of the Blake River Group, Rouyn–Noranda area, Abitibi, Quebec

1984 ◽  
Vol 21 (2) ◽  
pp. 220-231 ◽  
Author(s):  
Léopold Gélinas ◽  
Pierre Trudel ◽  
Claude Hubert
Keyword(s):  
Earth Element ◽  
Basaltic Magma ◽  
Volcanic Belt ◽  
Progressive Increase ◽  
Calc Alkaline ◽  
Significant Modification ◽  
Rhyolitic Magma ◽  
Tholeiitic Magma ◽  
Concentric Zone ◽  
Mafic Magmas

The effusive rocks of the Blake River Group in the Abitibi volcanic belt, Rouyn–Noranda region, belong to a bimodal sequence in which andesites and rhyolites clearly dominate. The identification of calc-alkaline and tholeiitic affinities is made upon examination of the major, trace, and rare earth element (REE) content. Thus, the andesites (58% normalized SiO2 value without volatiles) of the calc-alkaline units have average K (4800 ppm), Ba (160 ppm), and Rb (13 ppm) values that are greater than the average K (1800 ppm), Ba (130 ppm), and Rb (3 ppm) values for andésites (57% SiO2) that belong to associated tholeiitic units. Furthermore, tholeiitic andesites have distinctive average values of Ti (9600 ppm) and Y (40 ppm) that are higher than the average values of Ti (6700 ppm) and Y (25 ppm) of calc-alkaline andesites. An effective discrimination between the calc-alkaline and tholeiitic affinities is obtained using the Zr/Y and Ti/Zr ratios, which are, respectively, less than 4 and greater than 70 in andesites of the tholeiitic units.REE profiles of tholeiitic andesites are flat when compared with those of calc-alkaline andesites, which show an enrichment in light rare earths.The tholeiitic units of the Blake River Group are found in the proximity of the Porcupine-Destor and Larder Lake – Cadillac faults, the major faults of the region, and at the periphery of an ensemble of calc-alkaline units. Four of the five tholeiitic units are differentiated, showing an enrichment of iron passing from basalt to andesite. These units possess felsic variole-bearing flows, the result of an unmixing, which was probably responsible for the formation of minor associated quantities of porphyries and rhyolitic volcaniclastites.A progressive increase in the concentration of hygromagmatophile elements (REE, Zr, Nb) is observed in the tholeiitic units from the Pelletier unit beginning at the base and passing through the Trémoy, Destor, and Dufresnoy units, at the top of the Blake River Group. The calc-alkaline units are characterized by an alternation of rhyolitic complexes and calc-alkaline andesites. This cyclic repetition occurs without significant modification of the calc-alkaline andesite composition.It is proposed that the volcanism responsible for the formation of the Blake River Group was restricted to a concentric zone centring on a continental environment. Mafic magmas nourished the central reservoir where melting of the sialic crust took place. The rhyolitic magma occupying the upper part of this reservoir mixed with the basaltic magma, producing calc-alkaline andesites. Successive mantle melt products were also emplaced into subsidiary reservoirs peripheral to the central chamber. Injections of tholeiitic magma in the peripheral reservoirs underwent differentiation and unmixing during emplacement of a part of the magma at the surface.

scholarly journals The Role of Siliceous High-Magnesium Basalts during the Formation of a Neoproterozoic Mafic-Ultramafic Intrusion in the Tarim Craton (China)

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 662
Author(s):  
Xia ◽  
Xia ◽  
Ru
Keyword(s):  
Lithospheric Mantle ◽  
Basaltic Magma ◽  
Subcontinental Lithospheric Mantle ◽  
Crystallization Sequence ◽  
Zircon Age ◽  
Exposed Area ◽  
Tarim Craton ◽  
Ultramafic Intrusion ◽  
T Values

The Xingdi No.2 intrusion in the Kuluktag Block of northeastern Tarim Craton, which intrudes into the Palaeoproterozoic basement with an exposed area of ca. 12 km2, is an orthopyroxene-rich mafic-ultramafic intrusion in a continental rift setting. It consists of gabbros, pyroxenites, and peridotites, and exhibits a crystallization sequence of the principal rock-forming minerals from olivine, orthopyroxene, clinopyroxene, to plagioclase. The gabbros show a concordant SHRIMP U-Pb zircon age of 752 ± 5.4 Ma. In addition, the olivine grains have forsterite content values of 78–85 mole% and mostly contain low NiO, MnO, CaO, and Cr2O3. The rocks are relatively enriched in large ion lithophile elements and LREE, and depleted in HSFE, have non-radiogenic Pb, low εNd (t) values (−2.8 to −23), initial 87Sr/86Sr ratios (0.7059–0.7130). It could be concluded that the rocks represent an analogue of siliceous high magnesium basaltic magma originated by the partial melting of a hydrous and enriched subcontinental lithospheric mantle and contaminated by the continental crust.

scholarly journals ROLE OF PYROXENITE MANTLE IN MAGMA GENESIS OF THE OLIGOCENE BASALTS FROM THE NORTHERN PART OF EAST SIKHOTE ALIN

2020 ◽  
Vol 39 (6) ◽  
pp. 82-97
Author(s):  
A.Yu. Martynov ◽  
◽  
Yu.A. Martynov ◽  
A.I. Malinovskii ◽  
◽  
...  
Keyword(s):  
Basaltic Magma ◽  
Volcanic Belt ◽  
Sikhote Alin ◽  
Late Cenozoic ◽  
Magma Genesis ◽  
First Order ◽  
Geodynamic Environment ◽  
Magma Sources ◽  
Magma Compositions

Identification of magma sources as well as its role in creating the diversity of magma compositions still remains one of the fundamental petrological problems. In our work, on the basis of new comprehensive isotope-geochemical and mineralogical data, we made an attempt to reconstruct the contribution of pyroxenite mantle source in the Oligocene basaltic magma genesis of the northern part of East Sikhote Alin volcanic belt. The most important indicators of this source are significant variations the first order transit elements ratios (Zn/Fe = 11–17, Zn/Mn = 6–10, Cr/Ni (1.8–6) and concentration of Ni (2000–3600 г/т) in olivine. LIL elements behavior suggests the presence of amphibole in pyroxenite substrate. The data obtained can be useful for the correct reconstruction of the magma generation and the geodynamic environment of this territory at the Late Cenozoic.

Silicate melt inclusions in the cumulate minerals of gabbroic nodules from Stromboli Volcano (Aeolian Islands, Italy): main components of the fluid phase and crystallization temperatures

2002 ◽  
Vol 66 (6) ◽  
pp. 969-984 ◽  
Author(s):  
E. Salvioli-Mariani ◽  
M. Mattioli ◽  
A. Renzulli ◽  
G. Serri
Keyword(s):  
Melt Inclusions ◽  
Basaltic Magma ◽  
Fluid Phase ◽  
Silicate Melt ◽  
High Alumina ◽  
Variable Degree ◽  
Fe Content ◽  
Interstitial Material ◽  
Main Components

Abstract The studied gabbroic nodules occurring in the Petrazza pyroclastic rocks consist mainly of plagioclase (An95–87), olivine (Fo83-73) and clinopyroxene (Mg# 90–77), with subordinate opaques (Ti-magnetite) and amphibole (Mg-hastingsite), which constitute the cumulate minerals. Interstitial material has a relatively high, but variable, degree of vesicularity and consists of variable amounts of glass and quenched crystals of plagioclase (An71–55), amphibole, clinopyroxene and rare biotite, olivine and opaques. Silicate melt inclusions are abundant in the cumulate minerals, but complete homogenization to melt has been observed only in the inclusions occurring in clinopyroxene, where the temperatures of homogenization vary from 1134 to 1190°C. Microthermometric investigations of fluid inclusions and of the shrinkage bubble of the melt inclusions suggest that the magma contained CO2. The apparent scarcity of H2O indicates that this component was strongly partitioned into the magma at the time of crystallization of the investigated minerals; this is further supported by the occurrence of (1) daughter biotite- and amphibole-bearing inclusions which show that the H2O activity in the magma was sufficiently high to allow their crystallization, and (2) calcic plagioclase (An95–87) which can be crystallized from a high-alumina basaltic magma at pressure ≤2 kbar, temperatures in the range 1050–1100°C and in the presence of 3–4 wt.% of water (MELTS software simulations). The composition of the melt inclusions suggests that the hosting plagioclase, olivine and clinopyroxene crystallized from slightly different batches of magma. The S content in the melt inclusions of clinopyroxene and olivine is high (up to 0.41 wt.%). The presence of Fe-Cu(-Ni)-rich blebs of sulphide in plagioclase, olivine, amphibole, and locally in the melt inclusions too, further supports the important role of sulphur in the primitive magmas of the investigated gabbros. Small differences in redox conditions or in the Fe content of the melts favoured S mobilization as sulphide.

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