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Mechanisms and Timing of Pluton Emplacement in Taranaki Basin, New Zealand Using Three-Dimensional Seismic AnalysisCammans, Phillip C 01 October 2015 (has links) (PDF)
Several off-shore volcano-plutonic complexes are imaged in detail in the Parihaka 3D seismic survey in the Taranaki Basin of New Zealand. Three intrusions were analyzed for this study. Part of the Mohakatino Volcanic Centre (15 to 1.6 Ma), these intrusions have steep sides, no resolvable base reflectors, no internal stratification or structure, and they exhibit doming and faulting in the sedimentary strata above the intrusions. Deformation along the sides is dominated by highly attenuated, dipping strata with dips of 45° or higher that decrease rapidly away from the intrusions. Doming extends several hundred meters from the margins and produced many high-angle normal faults and thinned strata. The intrusions lie near normal faults with the Northern Intrusion lying directly adjacent to a segment of the Parihaka Fault. The Central Intrusion has localized normal faults cutting a graben in the area directly above the intrusion and extending in a NE-SW direction away from it. The Western Intrusion is near the western edge of the Parihaka 3D dataset and is not situated directly adjacent to extensional faults.Two distinct zones of intrusion-related faults developed around both the Northern and Central Intrusions representing two different stress regimes present during emplacement, a local stress field created by the intrusions during emplacement and the regional stress field. The deeper zones contain short radial faults that extend away from the intrusion in all directions, representing a local stress field. The shallower faults have a radial pattern above the apex of each intrusion, but farther from it, they follow the regional stress field and trend NE. Using our techniques to interpret radial faulting above both intrusions and the principal of cross-cutting relations, timing of emplacement for these intrusions are 3.5 Ma for the Northern Intrusion and between 5 and 4 Ma for the Central and Western Intrusions.Observed space-making mechanisms for the Northern and Central Intrusions include doming (~16% and 11%, respectively), thinning and extension of roof strata (~4% for both), and extension within the basin itself (29% and 12%). Stoping and floor subsidence may have occurred, but are not visible in the seismic images. Magmatic extension may have played a significant role in emplacement.Several gas-rich zones are also imaged within the seismic data near the sea-floor. They appear as areas of acoustic impedance reversal compared to surrounding sedimentary strata and have a reversal of amplitude when compared to the sea floor. The gas in these zones is either biogenic or sourced from deeper reservoirs cut by normal faults.
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Three-Dimensional Seismic Study of Pluton Emplacement, Offshore Northwestern New ZealandLuke, Jason Allen 22 February 2012 (has links) (PDF)
Detailed 3D seismic images of a volcano-plutonic complex offshore northwestern New Zealand indicate the intrusive complex lies in a relay zone between NE-trending en echelon normal faults. A series of high angle normal faults fan out from the margin of the Southern Intrusive Complex and cut the folded strata along the margin. These faults terminate against the margins of the intrusion, extend as much as 1 pluton diameter away from the margin, and then merge with regional faults that are part of the Northern Taranaki Graben. Offset along these faults is on the order of 10s to over 100 meters. Strata on top of the complex are thinned and deformed into a faulted dome with an amplitude of about 0.7 km. Steep dip-slip faults form a semi-radial pattern in the roof rocks, but are strongly controlled by the regional stress field as many of the faults are sub-parallel to those that form the Northern Taranaki Graben. The longest roof faults are about the same length as the diameter of the pluton and cut through approximately 0.7 km of overlying strata. Fault offset gradually diminishes vertically away from the top of the intrusion. The Southern Intrusive Complex is a composite intrusion and formed from multiple steep-sided intrusions as evidenced by the complex margins and multiple apophyses. Small sills are apparent along the margins and near the roof of the Southern complex. Multiple episodes of deformation are also indicated by a series of unconformities in the sedimentary strata around the complex. Two large igneous bodies make up the composite intrusion as evidenced by the GeoAnomaly body detection tool. The Southern Intrusive Complex has a resolvable volume of 277 km3. Room for the complex was made by multiple space-making mechanisms. Roof uplift created ~3% of the space needed. Compaction/porosity loss is estimated to have contributed 20-40% of the space needed. Assimilation may have created ~0-30% space. Extension played a major role in creating the space needed and is estimated to have created a minimum of 33% of the space. Floor subsidence and stoping may have occurred, but are not resolvable in the seismic survey.
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Pluton emplacement, aureole deformation and metamorphism, and regional deformation within the central White-Inyo Range, Eastern CaliforniaMorgan, Sven Soren 05 October 2007 (has links)
The central White-Inyo Range in eastern California is a deformed section of Neoproterozoic through Cambrian sedimentary rocks which has been intruded by granitic plutons associated with the Mesozoic Sierra Nevada intrusive suites to the west. My dissertation involves a characterization of the pre-plutonic regional deformation within the central White-Inyo Range and an understanding of the deformation of the wall rocks and magmas associated with pluton emplacement. The four chapters in this dissertation are a compilation of three published articles (two in journals, one in a field guide-book) and one manuscript.
The regional deformation was characterized by measuring the orientation of folds, bedding, and cleavage throughout the range, as well as utilizing these data from other authors and from published geologic maps. Synthesis of the data indicate that all regional structures pre-date the intrusions. The transition from regional structures to aureole structures reveals components of horizontal and vertical translation and rotation of bedding associated with forceful emplacement.
The Jurassic Eureka Valley-Joshua Flat-Beer Creek (EJB) composite pluton and Cretaceous Papoose Flat pluton, as well as the deformed metasedimentary rocks surrounding these plutons, have been examined in detail. Penetrative shortening of the wall rocks was studied in detail along three traverses across the aureole of the EJB pluton and from specific outcrops throughout the aureole. Sedimentary formations have been attenuated to approximately one third of their regional stratigraphic thicknesses. Strain is characterized by flattening and plane strain. Deformation mechanisms vary, but are dominated by intracrystalline slip and climb and by grain boundary sliding. Contact metamorphism is characterized by andalusite followed by sillimanite.
The internal fabric of the EJB pluton has been analyzed through the study of the anisotropy of magnetic susceptibility (AMS). Samples were collected at 210 locations ( 420 drill cores, approximately 1000 samples) throughout the pluton. Maps of the fabric and magnetic parameters reveal that magnetic fabrics cross-cut some compositional boundaries and parallel others. Comparison between the magnetic fabrics and the aureole structures indicate that the magma and surrounding plastic aureole deformed as a single unit during emplacement.
Detailed porphyroblast-matrix analysis within the concordant metasedimentary aureole rocks surrounding the Papoose Flat pluton indicates that inclusion trails within porphyroblasts can be used as strain markers to restore the aureole rocks to their prepluton emplacement position. The kinematics of rotation, the change in thickness and volume, and the amount of translation of the metasedimentary formations within the aureole have been determined using porphyroblast-matrix relationships, in combination with measurement of stratigraphic sections and whole-rock geochemical analyses.
The emplacement of the EJB and Papoose Flat plutons is modeled as occurring in two stages. The first stage is sill-like, producing a thermal aureole which lowers the viscosity of the surrounding sedimentary rocks. The second stage is forceful, causing upward and outward translation and rotation of the surrounding aureole. Porphyroblastmatrix relationships from the EJB and Papoose Flat pluton, and from the literature on the Ardara pluton, Ireland, and the Cannibal Creek pluton, Australia, support this two stage emplacement model for concordant plutons. / Ph. D.
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Stress and strain rate estimates associated with penetrative deformation of the Harkless quartzite aureole rocks, Papoose Flat Pluton, California/Using structure contour maps to analyze subsurface 3D fault geometry along segments of the Moine ThrustHeaverlo, Nicholas D. 03 June 2014 (has links)
Dynamically recrystallized quartz microstructures preserved in contact aureoles allow for stress and strain rate estimates associated with penetrative deformation of rocks surrounding pluton margins. Microstructural analysis of the Harkless quartzites surrounding the western margin of Papoose Flat pluton indicates that recrystallization occurred by grain boundary migration with mean recrystallized grain size ranging from 86-225 µm. The application of three calibrated piezometers results in differential stress estimates between ~11 and ~29 MPa. Published wet-quartzite dislocation creep flow laws combined with deformation temperature, water fugacity, and differential stress estimates infer strain rates that range from 1.2 x 10⁻¹⁴ s⁻¹ to 2.3 x 10⁻¹² s⁻¹.
In order to analyze 3D subsurface fault geometry along map-pattern curves (salients and recesses), a structure contour map of the Moine thrust, extending from the North Coast southwards to the Dundonnel area, was constructed from 1:50,000 scale British Geological Survey (BGS) maps by correlating between elevation control points constrained by the intersection of the fault trace with topographic contours. The structure contour map indicates significant lateral variation in fault geometry along the Moine thrust, with recesses associated with antiformal corrugations in the subsurface and salients characterized by planar geometries or broad synformal corrugations. Additionally, structure contour maps constructed on the Glencoul thrust, as depicted by original BGS maps confirms that the thrust segments to the NE and SW of Loch Glencoul are part of the same structure, rather than different structures separated by a lateral ramp as shown on more recent BGS maps. / Master of Science
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Heterogeneous internal fabric of the Mount Barcroft pluton, White Mountains, of eastern California: an anisotropy of magnetic susceptibility studyMichlesen, Karen Joyce 23 February 2004 (has links)
Anisotropy of magnetic susceptibility (AMS) have been used with great success for determining the internal structure and fabrics of Jurassic and Cretaceous plutons of felsic-intermediate compositions in the White-Inyo Range of eastern California. However, application of the AMS techniques to the Mount Barcroft pluton, located in the northern White Mountains, has yielded anomalous scalar and directional AMS data indicative of unprecedented heterogeneity on the meter-kilometer scale. The 165 Ma Mount Barcroft pluton is primarily of granodiorite composition and was intruded into the Barcroft Structural Break, a northeast striking, steeply dipping structure that juxtaposes Mesozoic metavolcanic rocks to the north against Proterozoic-Paleozoic metasedimentary rocks to the south.
Two oriented hand samples (A and B) were collected at each of 78 sites distributed on a 1 kilometer grid pattern across the 5 by 15 kilometer Mount Barcroft pluton and oriented cores were prepared from these hand samples for AMS analysis. Microstructure identification of single thin sections prepared for each sample site yielded primarily magmatic with minor solid-state structures. A highly heterogeneous distribution of scalar parameters (Km, P%, F%, L%, T) was documented both between sample sites and between the A and B cores at individual sites. The heterogeneity may be the result of complex mineral assemblages and the interaction between different magnetic mineral species ranging from single domain to pseudo-single domain to multidomain magnetite. More problematic are the directional parameters between A and B cores in orientation and fabric type (e.g. prolate and oblate susceptibility ellipsoids) occur which cannot be readily explained by a complex mineral assemblage. Different fabric types in A and B cores at individual sample sites could be the result of discrete, temporally unrelated, magma pulses of variable composition and viscosity. Heterogeneity of scalar and directional AMS parameters in the Mount Barcroft pluton, and its contrast with the homogeneous AMS signatures within similar age plutons to the south, may provide evidence for a previously unrecognized magma source beneath the northern White Mountains. / Master of Science
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Emplacement of the Santa Rita Flat pluton and kinematic analysis of cross cutting shear zones, eastern CaliforniaVines, John Ashley 05 January 2000 (has links)
This study documents the deformation history of the Santa Rita Flat pluton, eastern California, from the time of emplacement to post-emplacement transpressional shearing, and consists of manuscripts that make up three chapters. The first chapter addresses the emplacement of the Santa Rita Flat pluton using anisotropy of magnetic susceptibility (AMS). The second chapter describes the kinematic analysis of cross-cutting shear zones within the western margin of the pluton. The third chapter is an informal paper on the U/Pb dating of two sheared felsic dikes from the pluton.
AMS of the Santa Rita Flat pluton indicates that the paramagnetic and ferromagnetic minerals define a foliation which is arched into an antiformal structure in the central to southern parts of the pluton. The northern part of the pluton displays an east-west striking magnetic foliation which lacks a fold-like geometry. Previously published field mapping and petrologic surveys of the pluton and surrounding wall rocks indicate that the southern margin and northern part of the Santa Rita Flat pluton represents the roof and core of the pluton, respectively.
Integration of our analysis of the internal structure of the pluton with previously published work on the regional structure of the surrounding metasedimentary wall rocks, suggests that the pluton may have initially been intruded as a sill-like or "saddle reef" structure along a stratigraphically controlled mechanical discontinuity in the hinge zone of an enveloping regional-scale synform. Subsequent vertical inflation of this sill resulted in local upward doming of the overlying pluton roof and formation of the antiformal structure now observed at the current erosion level in the central-southern part of the pluton and overlying locally preserved roof rocks. No corresponding fold structure is indicated by AMS analysis in the northern part of the pluton, which is exposed at a deeper level, and represents a section closer to the pluton core.
Emplacement of the Santa Rita Flat pluton at 164 Ma overlaps in time with regional deformation at ~185 - ~148 Ma (Middle - Late Jurassic) recognized in the southern Inyo Mountains. Northwest trending folds are pervasive along the western flank of the Inyo and White Mountains, and may have accommodated strains at the lateral tips of thrust faults which crop out in the southern Inyo Mountains. We speculate that space for initial emplacement of the Santa Rita Flat pluton may have been produced by layer-parallel slip and hinge-zone dilation, accompanied by axis-parallel slip during formation of a regional scale thrust-related synform.
The Santa Rita shear system (SRSS) is composed of a series of discrete NW-SE striking steeply dipping shear zones that cut and plastically deform granitic rocks of the Santa Rita Flat pluton. The shear zones exhibit a domainal distribution of gently and steeply plunging stretching lineations, and are located at planar mechanical discontinuities between the granite and a series of felsic/mafic dikes which intrude the pluton. Mylonitized dikes within the shear zones contain syntectonic mineral assemblages not observed in dikes outside the shear zones, indicating that the dikes were intruded prior to shear zone development. Correlation with geometrically similar shear zones in the Sierra Nevada batholith to the west, suggests that the SRSS probably nucleated from a regional stress field in Cretaceous times (~90-78 Ma).
Strain is heterogeneous within the shear zones, with local development of protomylonite, mylonite, ultramylonite and phyllonite. Strain heterogeneity within the granite is attributed to fluid infiltration and chemical reaction and alteration of feldspar to fine-grained mica. These deformation-induced mineral changes would have resulted in progressive mechanical weakening over time of rocks within the SRSS. The phyllonites occur predominantly within steeply lineated shear zones and contain mylonitized foliation-parallel quartz veins. The pattern of c-axis preferred orientation in these quartz veins indicates that deformation within the shear zones occurred under plane strain conditions. Locally, quartz veins also cut the foliation planes, reflecting high pore fluid pressures during evolution of the SRSS. These cross-cutting quartz veins are also plastically deformed, and their c-axis patterns indicate weak constrictional strains. The orientation of the shear zones, together with their strain paths, are used to develop a transpressional kinematic model for development of the SRSS within a progressively rotating stress field. / Master of Science
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Vznik kompoziční a texturní zonálnosti mělce uložených granitoidních těles / The Origin of Compositional and Textural Zoning of Shallow-Level Granitoid PlutonsTrubač, Jakub January 2015 (has links)
The principal goal of this Ph.D. Thesis is to contribute to the research on formation of compo- sitional and textural zoning in shallow-level plutons. Processes responsible for emplacement of individual plutons/pulses and the origin of compositional zoning in are addressed in a great detail, from the pluton-scale down to the micro-scale. The main emphasis in the more focused part of this text is on a combination of various quanti- tative data sets from two well-selected plutons (the Říčany Pluton in the Central Bohemian Plu- tonic Complex and the Melechov Pluton in the Moldanubian Batholith). These detailed studies are supported by further research on the Štěnovice, Čistá and Ševětín plutons. In this way we cover the evolution of Variscan magmatism in the heart of Bohemian Massif in its entirety, from Late Devonian till Permian. The thesis is based on combining field and structural studies (including the anisotropy of mag- netic susceptibility, AMS), textural analysis, petrological, geochronological and geochemical methods with geophysical investigations. Mathematical approaches have been designed and applied to the interpretation of geochemical data, with potential applications to other igneous systems. I strongly believe that only such comprehensive studies on well-selected case examples have a...
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The petrogenesis of the Nelshoogte pluton: The youngest and most compositionally variable TTG pluton in the Barberton Granite-Greenstone TerrainMatsumura, Risa 04 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2014 / ENGLISH ABSTRACT: The compositions of tonalite-trondhjemite-granodiorite (TTG)-series rocks from the
Barberton Granite-Greenstone Terrain (BGGT) of Southern Africa vary in terms of major
element concentrations (leuco-trondhjemites to tonalites), trace elements (e.g. Sr, Rb, REE)
and degree of HREE depletion [(La/Yb)N ~ 0.50 - 121]. These geochemical parameters have
been interpreted to have significance for the geodynamic processes that produced TTG
magmas, particularly the depth of the source. In the Nelshoogte pluton, trondhjemite
emplacement occurred prior to and during (D2)-tectonism, and hornblende-bearing
tonalites/granodiorites occur as intrusive plugs within the trondhjemite. The geochemical
range portrayed by the ca. 3230 Ma Nelshoogte pluton covers almost the whole range
portrayed by all the TTG rocks of the BGGT, formed in the time interval 3550 to 3230 Ma.
U-Pb zircon dating reveals no significant differences in apparent ages between the
trondhjemites and tonalites of the Nelshoogte pluton; all lie between ca. 3240 and 3220 Ma.
A/CNK- and Ti-maficity correlations within the Nelshoogte pluton show behaviour typical of
I-type granitic rocks, confirming the metamafic character of the source and the involvement
of a peritectic garnet and clinopyroxene component in the magmas. The REE and traceelement
patterns resemble those of both ca. 3450 Ma TTG plutons and other ~ 3230 Ma TTG
plutons in the BGGT. This suggests that these different generations of TTG magmas were
generated from similar sources and by similar processes. The geochemical details are
consistent with a metamafic source which underwent melting at high pressure. This TTG
source was fundamentally different from the more potassic source/s that produced the
younger 3100 Ma granites. Additionally, high Zr/Sm and low Nb/Ta ratios in the Barberton
TTG rocks suggest that the Nelshoogte pluton originated as a group of chemically distinct
magmas, in a similar way to other ~ 3200 Ma TTGs. The protoliths of ~ 3450 Ma plutons and
~ 3200 Ma plutons might typically be rutile-bearing eclogite and/or 10 to 30 % garnet
bearing amphibolite.
The geochemical features of the Barberton TTGs suggest similar source compositions, but
different pressures of partial melting. For the ca. 3230 Ma plutons, the rocks of the Badplaas
pluton and the Nelshoogte trondhjemites/tonalites correspond to the high-pressure magmas,
as reflected by high Sr content, as well as high Sr/Y and (La/Yb)N ratios. In contrast, the
Kaap Valley TTGs and Nelshoogte granodiorites reflect the melting of a similar source at
moderate pressure. Furthermore, the Hf isotope data; Hft (+ 0.1 to + 1.9) and TDM model ages (3330 - 3230 Ma), suggest that the source rocks are ~ 20 to 100 Myr older than the
pluton. / AFRIKAANSE OPSOMMING: Die samestellings van tonaliet-trondhjemiet-granodioriet (TTG)-reeks gesteentes vanaf die
Baberton Graniet-Groensteen terrien (BGGT) van Suiderlike Afrika verskil in terme van
hoofelement konsentrasies (leuko-trondhjemiete tot tonaliete), spoorelemente (bv. Sr, Rb en
seldsameaarde-elemente(SAE)) en ook van swaar seldsameaarde-element (SSAE) uitputting
[(La/Yb)N ~ 0.50 - 121]. Deur interpritasie is daar vasgestel dat hierdie geochemiese
beperkings betekenis dra vir die geodinamiese prosesse wat TTG magmas produseer het, en
veral vir die diepte van die bron. In die Nelshoogte pluton het trondhjemiet inplasing voor en
gedurende (D2)-tektonisme voorgekom en horingblende-draende tonaliet/granodioriet kom
voor as intrusiewe proppe binne-in die trondhjemiet. Die geochemiese reeks wat uitgebeeld is
deur die ~ 3230 Ma Nelshoogte pluton ondersteun byna die hele reeks wat uitgebeeld is deur
al die TTG gesteentes van die BBGT wat gevorm het gedurende die tydsinterval 3550 tot
3230 Ma. U-Pb sirkoon datering openbaar geen merkwaardige verskille in ouderdomme
tussen die trondhjemiete en tonaliete van die Nelshoogte pluton nie. Al die ouderdomme lê
tussen 3240 en 3220 Ma.
A/CNK- en Ti-mafisiteit korrelasies binne die Nelshoogte pluton toon die tipiese gedrag van
I-tipe granitiese gesteentes, en bevestig sodoende die metamafiese karakter van die bron,
asook die betrokkenheid van ‘n peritektiese granaat en klinopirokseen component in die
magmas. Die seldsameaarde-element en spoorelement patroone lyk soos dié van albei ~ 3450
Ma plutons en ander ~ 3230 Ma TTG plutons in die BGGT. Dit stel voor dat hierdie
verskillende generasies van TTG magmas genereer was vanaf soortgelyke bronne en ook
deur soortgelyke prosesse. Die geochemiese besonderhede stem ooreen met ‘n metamafiese
bron wat smelting teen hoë druk ondergaan het. Hierdie TTG bron het fondamenteel verskil
van die meer kalium-ryke bron/ne wat die jonger 3100 Ma graniete prodiseer het. In ‘n
eenderse manier as ander ~ 3200 Ma TTG gesteentes, stel hoë Zr/Sm en lae Nb/Ta
verhoudings in die Baberton TTG gesteentes verder voor dat die Nelshoogte pluton ontstaan
het as ‘n groep chemies verskillende magmas. Die protoliete van ~ 3450 Ma plutons en ~
3200 Ma plutons mag dalk tipies rutiel-draende eklogiet en/of 10 tot 30% granaat draende
amfiboliet wees.
Die geochemiese aspekte van die Baberton TTGs stel eenderse bron komposisies, maar
verskillende drukke van gedeeltelike smelting voor. Vir die ~ 3230 Ma plutons stem die
gesteentes van die Badplaas pluton en die Nelshoogte trondhjemiete/tonaliete ooreen met die hoë druk magmas, soos weerspieël deur hoe Sr inhoud, sowel as hoe Sr/Y en (La/Yb)N
verhoudinge. In kontras weerspiel die Kaap Valley TTGs en Nelshoogte granodioriet die
smelting van ‘n eenderse bron teen matige druk. Verder stel die Hf isotoop data; Hft (+ 0.1
to + 1.9) en TDM model ouderdomme (3330 - 3230 Ma) voor dat die bron gesteentes ~ 20 to
100 Mjr ouer is as die pluton.
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Geochemical evidence for incremental emplacement of Palms pluton, southern CaliforniaRoell, Jennifer L. January 2009 (has links)
Thesis (M.S.)--Indiana University, 2009. / Title from screen (viewed on February 2, 2010). Department of Earth Sciences, Indiana University-Purdue University Indianapolis (IUPUI). Advisor(s): Andrew P. Barth, Gabriel M. Filippelli, Kathy Licht. Includes vitae. Includes bibliographical references (leaves 102-110).
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Petrologia do pl?ton granitico serra verde, por??o lestre do dom?nio serid?Costa, Lindaray Sousa da 19 June 2009 (has links)
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Previous issue date: 2009-06-19 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The study area is located at the eastern-central portion of the Serid? Belt, on the interface between the Serid? Group Metasediments and the crystalline basement rocks of
the Caic? Complex (RN). Petrographic and geochemical data allow us to define aspects related to the genesis and evolution of the Serra Verde Pluton magmas, which composes
the goal of this dissertation The Serra Verde Pluton is a stock with outcropping area of about 25 km?, which is intrusive into metasedimentary sequence and the basement gneisses. The pluton intrusion is sintectonic to the Brasiliano event, elongated along the NE direction, developing a cornue geometry. The rock is a monzogranite mainly composed by K-feldspar, plagioclase and quartz, which usually compose more than 85% of the modal analisys. The main mafic mineral is the biotite, while amphibole, sphene, epidote, opaque minerals, allanite, zircon and apatite occur as accessory minerals. It features still a latemagmatic paragenesis composed by chlorite, granular epidote, carbonates and muscovite,
developed through the percolation of late CO2 and H2O rich fluids. Chemically, the Serra Verde Pluton rocks may be classified as metaluminous, of calc-alkaline affiliation,
sometimes showing trondhjem?tic characteristics, with high Na2O (>4,5%), Sr (>400ppm) and Ba (>800ppm) and low K2O (≤3,0%), MgO (<1,0%), TiO2 (<0,5%), Rb (<90ppm), Y (≤16ppm) and Zr (≤13ppm). Micropetrographic evidences (mineral assembly and microtextures) indicate that the magma evolution occurred in moderated to high fO2 conditions, above the FMQ buffer. Thermo-barometric data obtained by minor elements geochemistry and the CIPW data, suggest a final/minimal pressure crystallization for the Serra Verde Pluton samples of about 3 to 5 kbar, liquidus temperature around 800o C, solidus temperature between 680o and 660o C. This data is compatible with those observed by many authors for the Neoproterozoic granites of the Serid? Belt. The group of analyzed data (Petrographic, microtextural and geochemical), suggests that the dominant process of the generation and evolution of the Serra Verde Granite magma was the fractional crystallization, probably from basement quartz-dioritic and tonalitic orthogneisses source / A ?rea estudada situa-se na por??o centro-leste da Faixa Serid?, na interface dos metassedimentos do Grupo Serid? e as rochas do embasamento cristalino do Complexo Caic? (RN). Dados petrogr?ficos e qeoqu?micos permitem definir os aspectos relativos ? g?nese e evolu??o do(s) magma(s) do Pl?ton Serra Verde, que constitui o alvo desta
Disserta??o de Mestrado. O Pl?ton Serra Verde constitui um stock com ?rea aflorante de aproximadamente 25 Km2, intrusivo na seq??ncia metassedimentar e nos gnaisses do embasamento. Este pl?ton corresponde a uma intrus?o sintect?nica ao evento brasiliano, alongada na dire??o
NE, com geometria en cornue. Trata-se de um monzogranito cuja assembl?ia mineral ominante ? composta por K-feldspato, plagiocl?sio e quartzo, que usualmente somam mais de 85% modal. Tem como m?fico principal a biotita, enquanto que anfib?lio itanita, ep?doto, opacos, allanita, zirc?o e apatita s?o os acess?rios. Apresenta ainda uma parag?nese tardi-magm?tica constiut?da de clorita, ep?doto granular, carbonato e muscovita, desenvolvida a partir da atua??o de flu?dos tardios ricos em CO2 e H2O. Quimicamente, as rochas do Pl?ton Serra Verde podem ser classificadas como metaluminosas, de filia??o c?lcio-alcalina, por vezes com caracter?sticas de associa??es trondhjem?ticas, com altos teores de Na2O (>4,5%), Sr (>400ppm) e Ba (>800ppm), e baixos teores de K2O (≤3,0%), MgO (<1,0%), TiO2 (<0,5%), Rb (<90ppm), Y (≤16ppm)
e Zr (≤13ppm). Evid?ncias micropetrogr?ficas (assembl?ias minerais e microtexturais) indicam que a evolu??o do magma ocorreu em condi??es de fO2 moderadas a elevadas, acima do
tamp?o FMQ. Dados termobarom?tricos obtidos atrav?s da geoqu?mica de elementos menores, tra?os e dados normativos CIPW sugerem uma press?o final/m?nima de cristaliza??o para as amostras do Pl?ton Serra Verde em torno de 3 a 5 kbar, temperatura do l?quidus em torno de 800?C, e temperatura do solidus em torno 680 a 660?C. Estes dados s?o compat?veis com os observados por diversos autores em granit?ides
neoproteroz?icos do Dom?nio Serid?. O conjunto de dados analisados (petrogr?ficos microtexturais e geoqu?micos),
sugerem ainda que o processo dominante na gera??o e evolu??o do magma do granito Serra Verde se deu por cristaliza??o fracionada, sendo ortognaisses quartzo dior?ticos a tonal?ticos do complexo do embasamento, prov?veis candidatos para sua fonte
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