The origin of magmatic layering in the High Tatra granite, Central Western Carpathians – implications for the formation of granitoid plutons

2012 ◽  
Vol 102 (2) ◽  
pp. 129-144 ◽  
Author(s):  
Aleksandra Gawęda ◽  
Krzysztof Szopa
Keyword(s):  
Magma Chamber ◽  
Mafic Magma ◽  
Crystal Nucleation ◽  
Tectonic Activity ◽  
Density Currents ◽  
Crystal Mush ◽  
Magma Flow ◽  
Large Numbers ◽  
Crystal Accumulation ◽  
Chamber Floor

ABSTRACTThe High Tatra granite intrusion is an example of a Variscan syn-tectonic, tongue-shaped intrusion. In some portions of the intrusion, structures occur which appear to be of sedimentary origin. These include structures similar to graded bedding, cross-bedding, troughs and flame structures, K-feldspar-rich cumulates and magmatic breccias. Formation of these structures might be related to changing magma properties, including crystal fraction, development of a crystal mush and a decrease in magma viscosity, stimulated by influx of mafic magma and high volatile content. The suggested processes in operation are: gravity-controlled separation, magma flow segregation, deposition on the magma-chamber floor, filter pressing and density currents stimulated by tectonic activity.%The formation of the sedimentary structures was also aided by the presence of large numbers of xenoliths that acted as a heat sink and influenced the thermal field in the intrusion, stimulating rapid cooling and crystal nucleation. Sinking xenoliths deformed the layering and, to some extent, protected the unconsolidated crystal mush from erosion by magma flowing past.%Areas with well-developed sedimentary magmatic structures can be viewed as having involved magma rich in crystals locally forming closely-packed networks from which residual melt was extracted by filter pressing, and preserved in leucocratic pods and dykes. Interleaved, non-layered granite may be interpreted to have formed from the magma with initially low crystal fractions.%It is suggested that the intrusion was formed from numerous magma injections representing different stages in the mixing and mingling of felsic and mafic sources. It solidified by gravitation-driven crystal accumulation and flow sorting on the magma chamber floor and on the surfaces of large numbers of xenoliths. Shear stress acting during intrusion might have influenced the formation of magmatic structures.

scholarly journals The Creation and Evolution of Crystal Mush in the Upper Zone of the Rustenburg Layered Suite, Bushveld Complex, South Africa

2019 ◽  
Vol 60 (8) ◽  
pp. 1523-1542 ◽  
Author(s):  
Z Vukmanovic ◽  
M B Holness ◽  
M J Stock ◽  
R J Roberts
Keyword(s):  
South Africa ◽  
Magma Chamber ◽  
Simple Shear ◽  
Bushveld Complex ◽  
Immiscible Liquid ◽  
Textural Analysis ◽  
Crystal Nucleation ◽  
Crystal Mush ◽  
Gravitational Loading ◽  
Crystal Accumulation

Abstract The Upper Zone of the Rustenburg Layered Suite of the Bushveld Complex contains the world’s largest Fe–Ti–V ± P deposit and formed from the last major injection of magma into the chamber. Quantitative textural analysis of Upper Zone rocks was undertaken to constrain the processes operating during mush formation and solidification, focussing on horizons with the greatest density contrast to isolate the effects of gravitational loading. We examined three magnetitite layers, together with their underlying and overlying anorthosites. The similarity of microstructures in anorthosites above and below the dense magnetitite layers suggests that the rocks were not affected by viscous compaction driven by gravitational loading. The magnetitite cumulate layers formed by crystal accumulation from a mobile crystal slurry dominated by the Fe-rich conjugate of an unmixed immiscible liquid. We suggest a new mechanism of crystal nucleation in deforming crystal-rich systems, driven by undercooling caused by cavitation as grains slide past each other during simple shear. We propose that the super-solidus deformation recorded in these rocks was caused by prolonged regional subsidence of the magma chamber at Upper Zone times.

Granites, dynamic magma chamber processes and pluton construction: the Aztec Wash pluton, Eldorado Mountains, Nevada, USA

2004 ◽  
Vol 95 (1-2) ◽  
pp. 277-295 ◽  
Author(s):  
Brian E. Harper ◽  
Calvin F. Miller ◽  
G. Christopher Koteas ◽  
Nicole L. Cates ◽  
Robert A. Wiebe ◽  
...  
Keyword(s):  
Magma Chamber ◽  
Debris Flows ◽  
Mafic Magma ◽  
Fractional Crystallisation ◽  
Accessory Mineral ◽  
Magma Chamber Processes ◽  
Second Stage ◽  
Crystal Accumulation ◽  
Melt Segregation ◽  
Aztec Wash Pluton

ABSTRACTThe mid-Miocene Aztec Wash pluton is divisible into a relatively homogeneous portion entirely comprising granites (the G zone, or GZ), and an extremely heterogeneous zone (HZ) that includes the products of the mingling, mixing and fractional crystallisation of mafic and felsic magmas. Though far less variable than the HZ, the GZ nonetheless records a dynamic history characterised by cyclic deposition of the solidifying products of the felsic portion of a recharging, open-system magma chamber.Tilting has exposed a 5-km section through the GZ and adjacent portions of the HZ. A porphyry is interpreted as a remnant of a chilled roof zone that marks the first stage of felsic GZ intrusion. Subsequent recharging by felsic and mafic magma, reflected by repeated cycles of crystal accumulation and melt segregation in the GZ and emplacement of mafic flows in the HZ, rejuvenated and maintained the chamber. Kilometre-scale lobes of mafic HZ material were deposited as prograding tongues into the GZ during periods of increased mafic input. Thus, they are lateral equivalents of the cumulate GZ granites with which they interfinger. Conglomerate-like units comprising rounded, matrix-supported intermediate clasts in cumulate granite are located immediately above the lobes. These ‘conglomerates’ appear to represent debris flows shed from sloping upper surfaces of the lobes. Thus, the GZ can be viewed as comprising distal facies, remote from the site of mafic recharging in the HZ, and the HZ as comprising proximal facies.Elemental chemistry suggests that the GZ cumulate granites represent a second-stage accumulation from an already evolved melt, and that coarse, more mafic, feldspar+biotite+accessory mineral ± hornblende rocks trapped between mafic sheets in the HZ are the initial cumulates. Fractionated melt accumulated roofward and laterally, and was the direct parent of the ‘evolved’ GZ cumulates. The most highly fractionated, fluid-rich melts accumulated at the roof.

scholarly journals Mechanisms controlling explosive-effusive transition of Teide-Pico Viejo complex dome eruptions.

2020 ◽  
Author(s):  
Olaya Dorado ◽  
Joan Andújar ◽  
Joan Martí ◽  
Adelina Geyer
Keyword(s):  
Magma Chamber ◽  
Magma Mixing ◽  
Mafic Magma ◽  
Main Body ◽  
Density Currents ◽  
Volcanic System ◽  
Effusive Activity ◽  
Tenerife Island ◽  
Explosive Phase ◽  
The One

<p>The Teide-Pico Viejo (PT-PV) stratovolcanoes constitute one of the major potentially active volcanic complexes in Europe. PT-PV was traditionally considered as non-explosive system however, recent studies (ie. García et al. 2014) have pointed out that the explosive character of phonolitic magmas, including plinian and subplinian eruptions and generation of pyroclastic density currents, have also been significant within the last 30 kyr volcanological record. This explosive activity is mostly associated to satellite dome vents, like the one studied in this work, Pico Cabras. Dome-forming eruptions usually present sudden transitions between explosive and effusive activity. A better knowledge of this type of eruptions and about the main mechanisms controlling the changes in eruptive dynamics is required to undertake a comprehensive volcanic hazard assessment of Tenerife Island. In this study, we conduct a petrological and mineral characterization of the different eruption phases of Pico Cabras (pumice and lava flow samples for the explosive and effusive activity, respectively) with the aim of determining the factors that control these changes in the volcanic activity. Products were characterized with Scanning Electrom Microscope, and mineral phases, glass and volatile species (F, Cl) were analysed with electron microprobe and micro-XRF. The pre-eruptive conditions of the magma (pressure, temperature and water dissolved in the magma) were determined first by using available geothermobarometers, geohygrometers (Masotta et al., 2013; Mollo et al., 2015) and compared to those retrieved by using available phase equilibria experiments from the literature (ie. Andújar and Scaillet, 2012).</p><p>Our results suggest the presence of a compositionally stratified magma chamber at 1 kbar±0.5kbar prior to Pico Cabras eruption in which the differences in the eruptive styles are controlled by the temperature and the amount of volatiles dissolved in the melt. The explosive phase is related to the upper part of the magma chamber at 725ºC±25ºC and 3,5-5 wt% H<sub>2</sub>O and the effusive phase with the main body of the chamber at 880ºC±30ºC and 2,5-3 wt% H<sub>2</sub>O. Feldspar zonations show that overturn events occurred in the different layers of the magma chambers (“self-mixing”) and suggest that the eruption was triggered by underplating of mafic magma without magma mixing. Chemical composition of some feldspars from the explosive phase are equivalent to those found in El Abrigo eruption, the last caldera-forming episode (ca. 190 ka), demonstrating that PT-PV volcanic system is still capable of producing evolved and very explosive magmas.</p><p>This research has been partially funded by a CSIC JaeIntro grant and the EC Grant EVE (DG ECHO Ref: 826292).</p>

Effects of Continents and Supercontinents on Organic Evolution

2004 ◽  
Author(s):  
John J. W. Rogers ◽  
M. Santosh
Keyword(s):  
Environmental Change ◽  
Environmental Stress ◽  
Tectonic Activity ◽  
Continental Margins ◽  
Organic Evolution ◽  
Ocean Ridges ◽  
Large Numbers ◽  
Local Species ◽  
Orogenic Belts ◽  
Shallow Seas

The earth’s organic life has changed continually for more than 3.5 billion years. This evolution may have resulted partly from environmental stress generated by tectonic activity within the earth and partly from processes independent of the earth’s interior. This chapter investigates these different effects in an attempt to determine the role that continents played in the evolution of organisms. Continents and tectonics associated with them may have influenced organic evolution in both active and passive ways. Active effects include several processes that partly controlled the earth’s surface environment. Climate change was caused partly by movements of continents and construction of orogenic belts. Continental rifting increased the area of shallow seas as new continental margins subsided. Changes in volume of ocean ridges and epeiric movements of continents caused marine transgressions and regressions. Temperatures of water in shallow seas increased or decreased as continents moved across latitudes. The major passive effects of continents and supercontinents result from their influence on diversity of organisms. When continents were broadly dispersed and occupied most latitudes, as on the present earth, this isolation resulted in shallow-water and subaerial families that contained numerous genera, genera with large numbers of species, and species divided among many different varieties. This diversity was clearly smaller at times when continents were aggregated into a few landmasses and particularly low when supercontinents permitted exchange of organisms throughout most of the world’s land and shallow seas. During times of major environmental stress, these differences would have restricted extinction of organisms to local species and genera during times of high diversity but might have permitted disappearance of whole orders and classes when diversity was low. Organic evolution was almost certainly affected by species diversity, but it may have occurred without any active control by tectonic processes. Although evolution probably occurs only when changing environments place stresses on organisms that enhance the competition among them, it is also possible that competition between organisms can cause evolution even without significant environmental change. Furthermore, some environmental change probably resulted from processes that are not related to the tectonics of the solid earth.

Insights into granite petrogenesis from quantitative assessment of the field distribution of enclaves, xenoliths and K-feldspar megacrysts in the Monte Capanne pluton, Italy

2008 ◽  
Vol 72 (4) ◽  
pp. 925-940 ◽  
Author(s):  
D. Gagnevin ◽  
J. S. Daly ◽  
G. Poli
Keyword(s):  
Field Study ◽  
Magma Chamber ◽  
Late Stage ◽  
Field Data ◽  
Quantitative Assessment ◽  
Mafic Magma ◽  
Crustal Assimilation ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Quantitative Analyses

AbstractA detailed field study to determine quantitatively the distribution of K-feldspar megacrysts, mafic microgranular enclaves (MME) and metasedimentary xenoliths has been carried out in the Monte Capanne pluton (Elba, Italy) with a view to evaluating the utility of this approach to petrogenetic investigations. Mafic microgranular enclaves are inferred to result from interactions between mafic and felsic magmas, while xenoliths attest to crustal assimilation occurring in the Monte Capanne magma chamber. In particular, we emphasize, based on our field data, that both processes are intimately linked, such that xenolith dissolution during assimilation was triggered by replenishment with hot mafic magma. It is suggested that the previously defined ‘San Piero’ and ‘San Francesco’ facies do not differ substantially, and are thus amalgamated and renamed as the ‘Pomonte’ facies. Results also indicate that the abundance of K-feldspar megacrysts is positively correlated with the volumetric abundance of MME in the Sant’ Andrea facies, which we link to a recharging, mingling and textural coarsening event that occurred at a rather late stage of magma-chamber evolution prior to emplacement. This study demonstrates how petrogenetic processes can be deciphered by detailed field quantitative analyses of granite-forming components, thus complementing geochemical investigations.

Petrology, age, and tectonic setting of the rapakivi-bearing Margaree pluton, Cape Breton Island, Canada: evidence for a Late Devonian posttectonic cryptic silicic-mafic magma chamber

2020 ◽  
Vol 57 (9) ◽  
pp. 1011-1029
Author(s):  
Gabriel Sombini dos Santos ◽  
Sandra M. Barr ◽  
Chris E. White ◽  
Deanne van Rooyen
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Magma Chamber ◽  
Magma Mixing ◽  
Tectonic Setting ◽  
Mafic Magma ◽  
Coarse Grained ◽  
Late Devonian ◽  
Cape Breton Island ◽  
Cape Breton

The Margaree pluton extends for >40 km along the axis of the Ganderian Aspy terrane of northern Cape Breton Island, Nova Scotia. The pluton consists mainly of coarse-grained megacrystic syenogranite, intruded by small bodies of medium-grained equigranular syenogranite and microgranite porphyry, all locally displaying rapakivi texture. The three rock types have similar U–Pb (zircon) ages of 363 ± 1.6, 364.8 ± 1.6, and 365.5 ± 3.3 Ma, respectively, consistent with field and petrological evidence that they are coeval and comagmatic. The rare earth elements display parallel trends characterized by enrichment in the light rare earth elements, flat heavy rare earth elements, moderate negative Eu anomalies, and, in some cases, positive Ce anomalies. The megacrystic and rapakivi textures are attributed to thermal perturbation in the magma chamber caused by the mixing of mafic and felsic magma, even though direct evidence of the mafic magma is mainly lacking at the current level of exposure. Magma evolution was controlled by fractionation of quartz, K-feldspar, and Na-rich plagioclase in molar proportions of 0.75:0.12:0.13. The chemical and isotopic (Sm–Nd) signature of the Margaree pluton is consistent with the melting of preexisting continental crust that was enriched in heat-producing elements, likely assisted by intrusion of mantle-derived mafic magma during Late Devonian regional extension. The proposed model involving magma mixing at shallow crustal levels in a cryptic silicic-mafic magma chamber during post-Acadian extension is consistent with models for other, better exposed occurrences of rapakivi granite in the northern Appalachian orogen.

Glass-bearing felsic nodules from the crystallizing sidewalls of the 1944 Vesuvius magma chamber

2000 ◽  
Vol 64 (3) ◽  
pp. 481-496 ◽  
Author(s):  
P. Fulignati ◽  
P. Marianelli ◽  
A. Sbrana
Keyword(s):  
Magma Chamber ◽  
Melt Inclusions ◽  
Mineral Chemistry ◽  
Glassy Matrix ◽  
Crystal Mush ◽  
Stratigraphic Sequence ◽  
Shallow Magma Chamber ◽  
Mineral Assemblages ◽  
Pressure Crystallization

AbstractIn the 1944 Vesuvius eruption, the shallow magma chamber was disrupted during the highly energetic explosive phases. Abundant cognate xenoliths such as subvolcanic fergusites and cumulates, hornfels, skarns and rare marbles occur in tephra deposits.Mineral chemistry, melt inclusions in minerals and glassy matrix compositions show that fergusites (highly crystalline rocks made of leucite, clinopyroxene, plagioclase, olivine, apatite, oxides and glass) do not correspond to melt compositions but result from combined sidewall accumulation of crystals, formed from K-tephriphonolitic magma resident in the chamber, and in situ crystallization of the intercumulus melt. Very low H2O contents in the intercumulus glass are revealed by FTIR and apatite composition. Whole rock compositions are essentially determined by the bulk mineral assemblages.Glass–bearing fergusites constitute the outer shell of the magma chamber consisting of a highly viscous crystal mush with a melt content in the range 20–50 wt.%. The leucite/(clinopyroxene+olivine) modal ratio, varies with the extraction order of magmas from the chamber, decreasing upwards in the stratigraphic sequence. This reflects a vertical mineralogical zonation of the crystal mush. These data contribute to the interpretation of the subvolcanic low–pressure crystallization processes at the magma chamber sidewalls affecting alkaline potassic magmas.

Magma chamber formation by magma intrusion into the Earth's crust

2020 ◽  
Author(s):  
Ivan Utkin ◽  
Oleg Melnik
Keyword(s):  
Magma Chamber ◽  
Flow Rate ◽  
Structural Features ◽  
Numerical Dissipation ◽  
Magma Chambers ◽  
Magma Intrusion ◽  
Magma Flow ◽  
Formation Of Cracks ◽  
Heating Up ◽  
Magma Flow Rate

<p>The main mechanism of transport of magma in the Earth’s crust is the formation of cracks, or dikes, through which the melt moves towards the surface under the action of buoyancy forces and tectonic stresses. Due to the structural features of the crust or external stress fields, dikes often do not reach the surface, but penetrate the localized region in which the rocks melt, leading to the formation of magmatic chambers, whose volume can exceed thousands of cubic kilometers. We present a model of the formation of a magma chamber during the intrusion of dikes at a given flow rate. The model is based on the solution of heat equation and considers the actual melting diagrams of magma and rocks. It Is shown that, in case of magmatic fluxes typical of island arc volcanoes, magma chambers are formed over hundreds of years from the beginning of magma intrusion. The influence of the magma flow rate, the size of the dikes and their orientation on the volume of the formed magma chamber and its shape was investigated. The size of the chamber significantly exceeds the area of dike intrusion due to the displacement of magma and rocks of the crust, their heating up and melting. To calculate displacement of rock and magma in a numerical simulation, a hybrid method based on PIC/FLIP interpolation is developed, making it possible to avoid unphysical mixing due to numerical dissipation, thus preserving the fine details of the formed magma chamber.</p><p>This work was supported by RFBR, project number 18-01-00352</p>

Sign in / Sign up

Export Citation Format

Share Document