A geochemical study of two peraluminous granites from south-central Iberia: the Nisa-Albuquerque and Jalama batholiths

1999 ◽  
Vol 63 (1) ◽  
pp. 85-104 ◽  
Author(s):  
J. A. Ramirez ◽  
L. G. Menendez
Keyword(s):  
Fractional Crystallization ◽  
Magma Mixing ◽  
Geochemical Data ◽  
Magmatic Differentiation ◽  
Peraluminous Granite ◽  
South Central ◽  
Geochemical Study ◽  
Peraluminous Granites ◽  
Magma Pulses ◽  
Fractional Crystallization Process

AbstractIn this paper we present new petrological and geochemical data for two peraluminous granite batholiths (Nisa Alburquerque and Jalama batholiths) representative of the ‘Araya-type’ granites of the Central-Iberian Zone. Both granites are composite with several facies (monzogranites and leucogranites) that can be grouped into two main granite units: the external units and central units. Intrusive relationships and lack of geochemical coherence between the central and external units indicate that they are not comagmatic but represent different pulses. The central units of both batholiths are petrologically and geochemically different. On the other hand, external units show a lot of similarities and are the main object of this study. The main characteristics of the external granites can be interpreted in terms of an incomplete fractional crystallization process of early mineral phases (plg + Kf + bt) which probably took place at the level of emplacement. Other possible mechanisms of magmatic differentiation (magma mixing, restite unmixing, sequential melting) can be discarded based on field, petrography and geochemical data. We propose that the ‘Araya-type’ granites are formed by the intrusion of distinct magma pulses (central and external). Further evolution within each pulse can be due to incomplete fractional crystallization possibly taking place at the emplacement level.

Field, geochemical, and isotopic evidence for magma mixing and assimilation and fractional crystallization processes in the Quottoon Igneous Complex, northwestern British Columbia and southeastern Alaska

1999 ◽  
Vol 36 (5) ◽  
pp. 819-831 ◽  
Author(s):  
J B Thomas ◽  
A K Sinha
Keyword(s):  
British Columbia ◽  
Fractional Crystallization ◽  
Magma Mixing ◽  
Parental Magma ◽  
Geochemical Data ◽  
Igneous Complex ◽  
Source Regions ◽  
Magmatic Body ◽  
Color Indices ◽  
Lower Crustal

The quartz dioritic Quottoon Igneous Complex (QIC) is a major Paleogene (65-56 Ma) magmatic body in northwestern British Columbia and southeastern Alaska that was emplaced along the Coast shear zone. The QIC contains two different igneous suites that provide information about source regions and magmatic processes. Heterogeneous suite I rocks (e.g., along Steamer Passage) have a pervasive solid-state fabric, abundant mafic enclaves and late-stage dikes, metasedimentary screens, and variable color indices (25-50). The homogeneous suite II rocks (e.g., along Quottoon Inlet) have a weak fabric developed in the magmatic state (aligned feldspars, melt-filled shears) and more uniform color indices (24-34) than in suite I. Suite I rocks have Sr concentrations <750 ppm, average LaN/YbN = 10.4, and initial 87Sr/86Sr ratios that range from 0.70513 to 0.70717. The suite II rocks have Sr concentrations >750 ppm, average LaN/YbN = 23, and initial 87Sr/86Sr ratios that range from 0.70617 to 0.70686. This study suggests that the parental QIC magma (initial 87Sr/86Sr approximately 0.706) can be derived by partial melting of an amphibolitic source reservoir at lower crustal conditions. Geochemical data (Rb, Sr, Ba, and LaN/YbN) and initial 87Sr/86Sr ratios preclude linkages between the two suites by fractional crystallization or assimilation and fractional crystallization processes. The suite I rocks are interpreted to be the result of magma mixing between the QIC parental magma and a mantle-derived magma. The suite II rocks are a result of assimilation and fractional crystallization processes.

scholarly journals Caracterização Petrográfica e Geoquímica da Parte Leste do Granito Europa, Distrito Mineiro de Pitinga, AM

2007 ◽  
Vol 34 (1) ◽  
pp. 77 ◽  
Author(s):  
MAURÍCIO PRADO ◽  
JOSÉ TADEU MAXIMINO MIRRAS FERRON ◽  
EVANDRO FERNANDES DE LIMA ◽  
ARTUR CEZAR BASTOS NETO ◽  
VITOR PAULO PEREIRA ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Genetic Relationship ◽  
Crystallization Process ◽  
Volcanic Rocks ◽  
Alkali Feldspar ◽  
Mineral Deposits ◽  
Geochemical Data ◽  
Principal Mechanism ◽  
Amazonian Region ◽  
Fractional Crystallization Process

The important mineral deposits of the Pitinga Mine, in the Amazonian region are related to A-type granites intruded in the Iricoumé Group. The Europa granite is one of these A-type rocks, intruded in the Iricoumé Group, which is represented by subaerial vulcanoclastic rocks (crystal-rich ignimbrites, thin massive tuffs and siltic tufaceous arenites) and minor hipabissal rhyolites. The volcanic rocks were probably generated in a caldera environment. The Europa granite is an alkali-feldspar peralkaline granite (hipersolvus) without genetic relationship with to the volcanic rocks of the Iricoumé Group, but it could have been generated during the resurgence stages. The petrographic and geochemical data attest that fractional crystallization process was the principal mechanism during the crystallization, which led to the generation of two different granitic facies. The Nb soil anomalies overprinted on the more differentiated facies are related to the astrophillite weathering.

scholarly journals GEOCHEMICAL CHARACTERISTICS OF THE ERENLERDAGI VOLCANICS, KONYA, CENTRAL TURKEY

2017 ◽  
Vol 50 (4) ◽  
pp. 2057
Author(s):  
C. Uyanık ◽  
K. Koçak
Keyword(s):  
Fractional Crystallization ◽  
Magma Mixing ◽  
Primitive Mantle ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
High K ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Central Turkey ◽  
Pyroclastic Fall

Late Miocene to Pliocene volcanism produced lava domes with mafic microgranular enclaves (MMEs), nuée ardentes and pyroclastic fall and flow (ignimbrites) deposits in the WSW and NW of Konya city. All samples are predominantly high K-calc alkaline in composition but calc-alkaline and shoshonitic composition also exist. The felsic volcanics are mainly dacite, andesite, basaltic trachyandesite and rare trachyandesite in compositon. But, the MMEs have basaltic andesite and andesite compositon. SiO2 increases with decreasing TiO2, FeOt, MgO and CaO, suggesting fractional crystallization of mafic minerals. All samples have fractionated chondritenormalised REE pattern (La/YbN: 6.7-18.1), and negative Eu anomaly (Eu/Eu*: 0.67- 0.89), indicating plagioclase fractionation. In primitive mantle-normalized spider diagram, the samples show an enrichment in large ion litophile elements (LILE) such as Cs and Ba, and depletion in high field strength elements (HFSE), e.g. Dy and Y. They show negative Nb, Ta and Ti anomalies, indicating a subduction signature for their genesis. Based on geochemical data, the volcanics are suggested to have been formed by Assimilation-Fractional Crystallization (AFC) and/or magma mixing process. Various geotectonic diagrams imply volcanic arc to post collisional setting for the samples.

The Mull Palaeogene dyke swarm: insights into the evolution of the Mull igneous centre and dyke-emplacement mechanisms

2010 ◽  
Vol 74 (4) ◽  
pp. 601-622 ◽  
Author(s):  
R. MacDonald ◽  
B. Bagiński ◽  
B. G. J. Upton ◽  
H. Pinkerton ◽  
D. A. MacInnes ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Dyke Swarm ◽  
Geochemical Data ◽  
Compositional Variation ◽  
Magmatic System ◽  
Magma Chambers ◽  
Rock Types ◽  
Basaltic Magmas ◽  
Silicic Magmas ◽  
Magma Pulses

AbstractGeochemical data are presented for five large Palaeogene dykes, members of the Mull swarm in southern Scotland and northern England (the Moneyacres, Hawick-Acklington, Barrmill, Muirkirk- Hartfell and Dalraith-Linburn dykes). The rock types range from basalt through andesite to dacite, although the range in individual intrusions is more restricted. The dykes are divisible into two groups; those where the compositional variation was generated by fractional crystallization of basaltic magmas, and those where it resulted from variable degrees of mixing of basaltic and silicic magmas. Several dykes are composite; the marginal facies can be more or less evolved than the central facies. The dyke magmas are thought to have originated from stratified magma chambers beneath the Mull centre and models are presented to show how the different components were derived from the chambers. Some dykes appear to have been terminated at or near the Southern Upland Fault, perhaps as a result of the chilling of early magma pulses by water in the fault. The Palaeogene dyke swarm is considerably more complex than previously recognized and has a significant input to models of the evolution of the Mull magmatic system.

Geochemistry of diorites and associated plutonic rocks of SE Jersey, Channel Islands

1987 ◽  
Vol 51 (360) ◽  
pp. 217-229 ◽  
Author(s):  
C. H. Key
Keyword(s):  
Fractional Crystallization ◽  
Magma Mixing ◽  
Solidus Temperature ◽  
Element Distribution ◽  
Basic Magma ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
High Field Strength ◽  
Plutonic Complex ◽  
The Status

AbstractThe plutonic complex in SE Jersey consists of a late Precambrian gabbro-diorite mass which has been intruded by several granites. The status of the diorites which, like the gabbros, often possess a layered structure, is not clear. New geochemical data, including rare earth and trace element analyses, suggest that acid-basic magma mixing was not responsible for the variety of intermediate rocks. Amphibole-controlled fractional crystallization of hydrous basic magma is also unlikely in view of the REE and HFS (high field strength) element distribution. The model which best fits all the available field, petrographic and geochemical evidence is one in which the chemical variation was initially produced by fractional crystallization of anhydrous basic magma and subsequently overprinted by granitic metasomatism. This superimposed calc-alkaline characteristics on the complex and produced hybrid diorites which, because they were above their solidus temperature, recrystallized with textures indicative of a magmatic origin.

The central Kenya peralkaline province: a unique assemblage of magmatic systems

2009 ◽  
Vol 73 (1) ◽  
pp. 1-16 ◽  
Author(s):  
R. Macdonald ◽  
B. Bagiński
Keyword(s):  
Fractional Crystallization ◽  
Magma Mixing ◽  
Experimental Studies ◽  
Liquid Immiscibility ◽  
Element Distribution ◽  
Low Viscosity ◽  
South Central ◽  
High Silica ◽  
Silicate Liquid Immiscibility ◽  
Central Kenya

The review focuses on the evolution of five contiguous peralkaline salic complexes in the south-central Kenya Rift Valley, stressing new developments of general significance to peralkaline magmatism. The complexes have evolved dominantly by combinations of fractional crystallization and magma mixing; volatile-melt interactions, remobilization of plutonic rocks and crystal mushes, and carbonate-silicate liquid immiscibility have been additional petrogenetic processes. Geochemical and experimental studies have shown that pantelleritic magmas can be generated by fractional crystallization of trachyte and high-silica rhyolite. Melts of comenditic composition were also formed by fractionation of trachyte but also locally by partial meltingof syenites. Studies of apparent partition coefficients have provided some of the first data on element distribution between phenocrysts and peralkaline silicic melts. Compositional zonation has been ubiquitous in the complexes, probably a result of the very low viscosity of the magmas.

scholarly journals PETROLOGY - GEOCHEMISTRY AND METALLOGENESIS OF VOLCANIC ROCKS IN THE PETROTA GRABEN/MARONIA, W.THRACE

2004 ◽  
Vol 36 (1) ◽  
pp. 482 ◽  
Author(s):  
Κ. Αρίκας ◽  
Π. Βουδούρης ◽  
M. R. Kloos ◽  
Ch. Tesch
Keyword(s):  
Fractional Crystallization ◽  
Magma Mixing ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
Mixing Processes ◽  
Geochemical Study ◽  
High K

The penological, mineralogical and geochemical study of tertiary volcanic rocks from Petrota Graben/Maronia, resulted in the distinction of the following pétrographie groups: a) a high-K calcalkaline group (andesites-dacites), b) a shoshonitic group (shoshonitic andésites, trachytic lavas, c) rhyodacitic ignimbrites and ignimbritic tuffs with high-K calc-alkaline to shoshonitic affinity, and d) rhyolites. The shoshonitic volcanic rocks and the rhyolites are probably originated from the neighbouring Maronia plutonio complex. In addition the calc-alkaline group is related to similar volcanics outcroping in the Mesti-Kassiteres area (the northeastern extension of the Graben). The petrogenesis of the volcanic rocks of the Petrota gragen is attibuted to fractional crystallization and/or magma mixing processes. Epithermal style mineralizations in Mavrokoryfi, Perama Hill and Odontoto are believed to be genetically related to the rhyolitic magmatism in the area.

scholarly journals Generation of the Mt Kinabalu Granite by Crustal Contamination of Intraplate Magma Modelled by Equilibrated Major Element Assimilation with Fractional Crystallization (EME-AFC)

2019 ◽  
Vol 60 (7) ◽  
pp. 1461-1487 ◽  
Author(s):  
A Burton-Johnson ◽  
C G Macpherson ◽  
C J Ottley ◽  
G M Nowell ◽  
A J Boyce
Keyword(s):  
Oxygen Isotope ◽  
Fractional Crystallization ◽  
Major Element ◽  
Crustal Contamination ◽  
Mafic Magma ◽  
Isotope Ratios ◽  
Geochemical Data ◽  
Magmatic Differentiation ◽  
Clear Trend ◽  
Mount Kinabalu

AbstractNew geochemical data are presented for the composite units of the Mount Kinabalu granitoid intrusion of Borneo and utilised to explore the discrimination between crustal- and mantle-derived granitic magmas. The geochemical data demonstrate that the units making up this composite intrusion became more potassic through time. This was accompanied by an evolution of isotope ratios from a continental-affinity towards a slightly more mantle-affinity (87Sr/86Sri ∼0·7078; 143Nd/144Ndi ∼0·51245; 206Pb/204Pbi ∼18·756 for the oldest unit compared to 87Sr/86Sri ∼0·7065, 143Nd/144Ndi ∼0·51250 and 206Pb/204Pbi ∼18·721 for the younger units). Oxygen isotope ratios (calculated whole-rock δ18O of +6·5–9·3‰) do not show a clear trend with time. The isotopic data indicate that the magma cannot result only from fractional crystallization of a mantle-derived magma. Alkali metal compositions show that crustal anatexis is also an unsuitable process for genesis of the intrusion. The data indicate that the high-K units were generated by fractional crystallization of a primary, mafic magma, followed by assimilation of the partially melted sedimentary overburden. We present a new, Equilibrated Major Element -Assimilation with Fractional Crystallization (EME-AFC) approach for simultaneously modelling the major element, trace element, and radiogenic and oxygen isotope compositions during such magmatic differentiation; addressing the lack of current AFC modelling approaches for felsic, amphibole- or biotite-bearing systems. We propose that Mt Kinabalu was generated through low degree melting of upwelling fertile metasomatized mantle driven by regional crustal extension in the Late Miocene.

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