Academic literature on the topic 'Metaluminous'

U–Pb zircon crystallization ages determined by isotope dilution – thermal ionization mass spectrometry (ID–TIMS) and laser ablation microprobe – inductively coupled plasma – mass spectrometry (LAM–ICP–MS) for 13 intrusive units in the Neoarchean Snare River terrane (SRT) provide tight constraints on the timing of crust formation and orogenic evolution. Seven metaluminous plutons were emplaced over ~80 Ma from ca. 2674 to 2589 Ma, whereas six peraluminous bodies were emplaced in a ~15 Ma interval from ca. 2598 to 2585 Ma. A detrital zircon study yielded an age spectrum with peaks correlative with known magmatic events in the Slave Province, with the ca. 2635 Ma age of the youngest detrital zircon population providing a maximum estimate for the onset of sedimentation. This age contrasts with evidence for pre-2635 Ma sedimentation elsewhere in the SRT, indicating that sedimentation was protracted and diachronous. Evolution of the SRT can be subdivided into four stages: (i) 2674–2635 Ma — formation of a metaluminous protoarc in a tonalite–trondhjemite–granodiorite (TTG) – granite–greenstone tectonic regime (TR1) and coeval with early turbidite sedimentation; (ii) 2635–2608 Ma — continued turbidite sedimentation, D1/M1 juxtaposition of turbidites and protoarc lithologies prior to ~2608 Ma, and metaluminous granitoid plutonism; (iii) 2608–2597 Ma — onset of TR2, collision of Snare protoarc with Central Slave Basement Complex, D2/M2 crustal thickening and mid-crustal granulite-facies metamorphism, sychronous with metaluminous and peraluminous plutonism; and (iv) 2597–2586 Ma — orogenic collapse, D3/M3 mid-crustal uplift, granulite-facies metamorphism, and waning metaluminous and peraluminous plutonism. The distribution of igneous rocks yields an "orogenic stratigraphy" with an older upper crust underlain by a younger synorogenic mid-crust. These data can be used to provide constraints for the interpretation of the Slave – Northern Cordillera Lithospheric Evolution (SNORCLE) Lithoprobe transect.

This study investigates basin-type granitoid samples from the north-eastern margin of the Kumasi Basin in Ghana to establish their source and geodynamic setting. Petrographic analysis, TAS and A/NK-A/CNK plots classify the granitoids as metaluminous quartz diorite, metaluminous granodiorite, and peraluminous monzogranite; and exhibiting I-type signatures. These rocks are formed by magma differentiation and/or partial melting at various stages. Distribution patterns of incompatible elements and the positive Eu/Eu* anomalies of 1.15 and 1.47 exhibited by quartz diorite and granodiorite, respectively, the values suggest the rocks crystallized from melts formed in a water-saturated environment. The negative Eu/Eu* anomaly exhibited by monzogranite indicate fractionation of plagioclase in the final stages of the magma evolution. The water-rich environment is probably due to dewatering of the basin’s foreland volcaniclastic sediments during regional subsidence, burial and metamorphism. K2O enrichments and wide variations suggest that the granodiorite and monzogranite are formed from fractional crystallization and/or crustal assimilation of the continental crust by under-plating dioritic magma. The higher Al2O3/TiO2 enrichment and the shift from metaluminous to peraluminous in the monzogranite suggest a longer residence time within the continental crust, during which fractional crystallization and the assimilation of pre-existing crustal components into the dioritic magma that resulted in the formation of the monzogranite. The study requires replication at other areas within the basin to generate enough data to enhance metallogenic studies in the terrain.

The Taquarembo Plateau, situated in the southwestern part of Sul-rio-grandense shield, is part of Camaquã Basin, that was formed at the end of the post-collisional stage in Brasiliano/Pan-Africa event, Neoproterozoic in age. This plateau is composed of volcanic and shallow intrusions, related to a silica-saturated alkaline series, ranging from alkaline metaluminous basalt to comendiitic flows, known as Taquarembo Volcano-Plutonic Association. The faciological identification leads to the reconstruction of the volcanic pile, formed from the base to the top by: particulated flows (ignimbrites and reo-ignimbrites); ressedimented syneruptive deposits; surge and fall horizons, closely associated with alkaline metaluminous lava flows (basalts, mugearites, rhyolites); and peralkaline lava flows (comendiites), and shallow intrusions of quarz monzonite and syenite that crosscut the volcanic pile. The facies identification suggests a highly explosive volcanic regime, under sub-aerial condition, in a close association with the feeder necks.

Collision-related rocks intrude metamorphic rocks overthrust by ophiolitic units to make up the Central Anatolian Crystalline Complex. A wide variety of rock types were produced by the latest Cretaceous magmatism in the complex. These rocks can be divided into three distinct units: (1) calc-alkaline (Ağaçören, Behrekdağ, Cefalıkdağ, Çelebi, Ekecikdağ, Halaçlı, Karamadazı, Kösefakılı, Terlemez, Üçkapılı, Yozgat); (2) sub-alkaline (Baranadağ); and (3) alkaline (Atdere, Davulalan, Eğrialan, Hamit, İdişdağı, Karaçayır). The calc-alkaline rocks are metaluminous/peraluminous I- to S-type plutons ranging from monzodiorite to granite. The sub-alkaline rocks are metaluminous I-type plutons ranging from monzonite to granite. The alkaline rocks are metaluminous to peralkaline plutons, predominantly A-type, ranging from foid-bearing monzosyenite to granite. These plutons crystallized under varying pressures (5.3–2.6 kbar) and a wide range of temperatures (858–698 °C) from highly oxidized magmas (log fO2 −17 to −12). All intrusive rocks display enrichment in LILE and LREE compare to HFSE and have high 87Sr/86Sr and low 143Nd/144Nd ratios. These characteristics indicate that these rocks are derived from a mantle source containing large subduction components, and have experienced assimilation coupled with fractional crystallization (AFC) during uprise through crust. The coexistence of calc-alkaline and alkaline magmatism in the complex may be ascribed to mantle source heterogeneity before collision. Either thermal perturbation of the metasomatized lithosphere by delamination of the thermal boundary layer or removal of a subducted plate (slab breakoff) are the likely mechanisms for the initiation of the collision-related magmatism in the complex.

The main lithological units which occur in the "Cabo Frio Tectonic Fragment" are orthogneisses and paragneisses. The orthogneisses have granitic-granodioritic-tonalitic compositions, with amphibolitic enclaves and intercalations and are cutted by granitic aplites. The paragneisses are metapelites, with intercalations of amphibolite, quartzites and calc-silicate rocks, metamorphosed in upper amphibolite facies, in intermediate pressure conditions. Geochemically, the orthogneisses correspond to a metaluminous high-K calc-alkalic series, with monzogabbro, quartz-monzodiorite and monzonite compositions. Otherwise, the petrography indicates a low-K calc-alkalic series, suggesting a pre-collisional granitoids series related to oceanic crust subduction. A divergence between the compositions obtained by the petrography and geochemistry can be the result of problems in the analyses of alkalies. The amphibolites, associated to the orthogneisses, also present calc-alkalic metaluminous character, with basaltic and andesitic compositions, suggestive of orogenic emplacement. The paragneisses show compositions varying between lithoarenite and arkoses, with peraluminous character, probably deposited in a continental are or ative continental margin environment.

The classical Al-in-hornblende barometer has been very successful in determining the depth of intrusion of the metaluminous cordilleran granitoid plutons that bear the buffering assemblage at near solidus conditions: horn-blende-biotite-plagioclase-orthoclase-quartz-sphene-two Fe-Ti-oxides (or one Fe-Ti oxide + epidote)-melt-vapor [...]

Petrographical and geochemical study, consistent with observed field relations show that the Boula Ibi syn- and post-kinematic granitoids in north Cameroon, occurred in banded gneisses. These syn- and post-kinematic granitoids consist of deformed monzonites typified by its granoblastic texture, diorites, syenites, granites and basic xenoliths of dioritic and monzonitic composition. They are calc-alkaline, hyperpotassic, metaluminous to slightly peraluminous and I-Type granitoids. They display high content in Fe2O3 + MgO + CaO (2.16 – 23.24 %) that reveals their intermediate affinity, magnesian and metaluminous character whilst the low A/CNK (< 1.1) content indicates their mantle origin. Harker diagrams and La/Sm vs La define the fractional crystallization and partial melting as the two main processes that led the geodynamic evolution of the Boula Ibi syn- and post-kinematic granitoids. These are consistent with low-content of Cs, Ta, Nb, Tb and Hf, supporting high melting rates ranging between 20 and 40% as well as molar Al2O3/(MgO + FeOt) vs CaO/(MgO + FeOt) plot showing magmatic evolutions from metabasaltic and metagreywackes sources.

An Upper Cambrian-Ordovician (490-460 Ma) batholith crop out along the Cordón de Lila and Sierra de Almeida, in the Antofagasta region, northern Chile, which belongs to the Famatinian arc. Two plutonic rock types can be distinguished: granodiorites and monzogranites. The first lithology is positioned along an occidental fringe in as much the second is located along an oriental part of the batholith. The main geochemical difference between the two lithologies is the enrichment in silica and K of the second with respect of the first one. Most of the granodiorites are metaluminous or are located between the metaluminous and peraluminous fields. The monzogranites are mostly peraluminous. The chemical composition of the plutons (mayor and trace elements and rare earth elements) allow to infer a common origin for both groups, from a mafic magma that evolved by fractional crystallization. The difference in composition between both lithologies, specially the meta or peraluminous character, can be explained by means a different degree of interaction of the original magma with the felsic crustal rocks.

The 57 m.y. Middle Fork Plutonic Complex (M FPC) intrudes Paleozoic metasedimentary rocks south of the Farewell Fault zone in the north-central Alaska Range. Though spatially related to the late Cretaceous - Early Tertiary subduction-related Alaska Range batholith, MFPC is more characteristic of an extensional or anorogenic setting. A swarm of basalt, hawaiite and rhyolite dikes east of the complex intruded, and was intruded by, the plutonic rocks. Approximately 30% of the exposed rock in the 125 km² complex is hedenbergite - fayalite syenite, ≃20% is peralkaline arfvedsonite - biotite alkali-feldspar granite (AF granite), and ≤20% is pyroxene - olivine - biotite gabbro. The rest is a mixed unit including clinopyroxene - biotite - amphibole diorite, and hornblende - biotite granite (HB granite). K-Ar and Rb-Sr radiometric dating of rock types shows that they are coeval. Their close spatial and temporal relationships led to complex magmatic interactions. Calculated initial ⁸⁷Sr/⁸⁶Sr for gabbro and diorite group around 0.705 to 0.706. HB granites are heterogeneous, but fall mostly around 0.707 to 0.708. Hypersolvus syenites and AF granites form an isochron with initial ⁸⁷Sr/⁸⁶Sr of 0.70965. These groupings suggest that at least three different magmas formed the MFPC; scatter of isotopic data reflects mu- tual contamination and assimilation. Trends in whole rock and mineral chemistry also reflect interactions between the magmas. Consanguinous hypersolvus syenite and AF granite mineralogy appears to be controlled by fluorine in the magma chamber. Magmatic mineral assemblages reflect increasingly reduced magmatic conditions; subsolidus oxidation, indicated by mafic mineralogy and cathodoluminescence, is due to magmatic process rather than introduction of external components. Eruptive stratigraphy, as predicted by intrusive history of MFPC, compares favorably with volcanic stratigraphies of peralkaline volcanic systems worldwide, and MFPC may be modelled as the root zone of a peralkaline volcanic system. The common absence of mafic volcanism during peralkaline volcanic activity may be due to entrapment of mafic magmas within the peralkaline magma chamber. The result of this entrapment is seen at the present level of erosion of MFPC, as extensive mafic enclave swarms and pull-apart dikes within syenites in the pluton's core.<br>Ph. D.

Os Plutons Palermo (ca. 250 km2) e Rio Negro (ca. 130 km2) afloram na região Alto Rio Negro (PR) e fazem parte da Província Graciosa, uma província Neoproterozóica (ca. 580 Ma) constituída por granitos e sienitos na região S-SE do Brasil. Em ambos os plutons afloram variedades de rochas graníticas, predominantes, e gabro-dioríticas, bem como rochas híbridas, principalmente granodioritos. Estes plutons apresentam zonamento em geral bem marcado, que é tipicamente inverso caso do Pluton Rio Negro. As rochas graníticas principais correspondem a sieno- e monzogranitos predominantes e álcali-feldspato granitos e quartzo monzonitos subordinados de natureza metaluminosa a levemente peraluminosa. São rochas com estruturas maciças e texturas variadas que apresentam como associação mineral máfica típica hb + bi ± all + zr + ap ± ti + mt + ilm); as rochas gabro-dioríticas incluem gabro-dioritos e quartzo monzogabro-dioritos metaluminosos com estruturas maciças e granulações fina a média, caracterizadas pela associação cpx ± opx + hb + bt ± ti ± ap ± zr. A composição dos plagioclásios nestas rochas varia no intervalo de labradorita a andesina. As rochas híbridas são principalmente granodioritos que se caracterizam por uma variedade de estruturas e texturas indicativas de desequilíbrio, compatíveis com processos de coexistência e mistura parcial entre líquidos ácidos e básico-intermediários que formaram os granitos principais e os gabro-dioritos. Estas rochas são mais comuns no Pluton Rio Negro. A associação mineral máfica é similar, mas com abundâncias distintas de fases, à observada para os granitos principais. Nas rochas graníticas os anfibólios são Fe-hornblenda e Fe-edenita, com valores 0,65 < fe# < 0,95, os valores mais elevados ocorrendo nos álcali-feldspato granitos, as biotitas apresentam 0,71 < fe# < 0,99, observando-se que o componente annítico é também maior nestas últimas rochas. No caso das rochas gabro-dioríticas, os valores fe# variam entre 0,48 e 0,59, 0,41 e 0,56, 0,47 e 0,53 e 0,54 a 0,57 para ortopiroxênio, clinopiroxênio, anfibólio e biotita, respectivamente. As composições médias de orto- e clinopiroxênio coexistentes são \'Wo IND.46\'\' En IND.30\'\' Fe IND.24\' e \'Wo IND.3\'\' En IND.42\'\'Fe IND.55\' e a sugerem uma possível afinidade toleítica, ou cálcio-alcalina, para magma original. Os padrões de elementos terras raras revelam fatores de enriquecimento entre 1-10, 50-70, 100-300 em relação à composição condrítica para ortopiroxênio, clinopiroxênio e anfibólio nas rochas estudadas, com fracionamento bem marcado dos elementos leves em relação aos pesados no ortopiroxênio, não observado no caso de clinopiroxênio e anfibólio. Todos os padrões são caracterizados por anomalia negativa bem marcada de Eu. As pressões de cristalização dos magmas foram estimadas entre 1-3,5 kbar, mas os valores acima de ca. 2 kbar possivelmente não tenham significado real, dadas as composições mais ferroanas dos anfibólios. Temperaturas de saturação de zircão e/ou apatita e de equilíbrio entre orto- e clinopiroxênio, anfibólio-plagioclásio indicam intervalos de cristalização entre ca. 1000 e 750° C para as rochas gabro-dioríticas e entre ca. 900 e 670° C para os granitos principais. As paragêneses minerais e os valores obtidos para o número fe# em biotita em equilíbrio com feldspato alcalino e magnetita apontam para condições de cristalização relativamente oxidantes para as rochas félsicas, exceto os álcali-feldspato granitos, e máfico-intermediárias, superiores ao tampão QFM.<br>The Palermo (ca. 250 km2) and Rio Negro (ca. 130 km2) Plutons crop out in the so called Alto Rio Negro region , Parana state, making part of the Graciosa Province, a NeoProterozoic province (ca. 580 Ma) constituted by granites and syenites in S-SE Brazil. The plutons are made predominant granitic rocks, gabbro-diorites, as well as hybrid rocks constituted mainly by granodiorites. Both plutons show compositional a zoning pattern, which is inversed in the case of the Rio Negro Pluton. The main granitid rocks are mainly metaluminous to slightly peraluminous syeno- and monzogranites with subordinate quartz monzonites and alkcali-feldspar granites. They show a massive structure and a variety of textures, with hb + bi ± all + zr + ap ± ti + mt + ilm as the typical mafic mineral association. Gabbro-dioritic rocks include fine- to medium-grained metaluminous gabro-diorites and quartz monzogabrros and diorites with massive strucure characterized by the mafic mineral associations with cpx ± opx + hb + bt ± ti ± ap ± zr. In these rocks, the plagioclase compositions vary between labradorite and andesine. Hybrid rocks are mainly granodiorites characterized by several strucures and textures indicative of desiquilibrium and mingling/partial mixing between the silicic and basic-intermediate melts that formed the mainn granites and the gabbro-diorites. Such rocks are more abundant in the Rio Negro Pluton. The mafic mineral association is similar, but in contrasted relative abundance, to the ones found in the main granites. In the main granites the amphiboles are Fe-horblende and Fe-edenite, with 0.65 < fe# < 0.95, the higher among these values appearing in the alkali-feldspar granites. Biotite present 0.70 < fe# < 0.99 and the annitic component are also higher in the later rocks. In the case of the gabbro-dioritic rocks, the fe# numbers range between 0.48 and 0.59, 0.41 and 0.56, 0.47 and 0.53 and 0.54 and 0.57 in ortopyroxene, clinopyroxene, amphibole and biotite, respectively. The averaged compositions of coexisting orto- and clinopyroxene are \'Wo IND.46\'\'En IND.30\'\'Fe IND.24\' and \'Wo IND.3\'\'En IND.42\'\'Fe IND.55\' and suggest a tholeiitic or calk-alkaline nature of the original melts. Rare earth element patterns reveal enrichment factors up to 1-10, 50-70, 100-300 relative to the chondritic composition in ortopyroxene, clinopyroxene and amphibole, respectively, with a well marked fractionation of the heavy over the light rare earths in the case of the ortopyroxene, a feature not observed in clinopyroxene and amphibole. All patterns show a notable Eu negative anomaly. Melts crystallization pressures were estimated to be between 1 and 3.5 kbar; however values higher than ca. 2 kbar seems to be unrealistic given the ferroan compositions of some amphiboles. Zircon and apatite saturation temperatures coupled with ortopyroxene-clinopyroxene and amphibole-plagioclase equilibrium temperatures suggest crystallization intervals between ca. 1000 - 750° C in the case of the gabbro-diorites and ca. 900 - 670° C in the case of the main granites. Mineral paragenesis and fe# values in biotite in equilibrium with alkali-feldspar and magnetite suggests relative oxidizing crystallization conditions for the acid and basic-intermediate melts, higher than the QFM buffer, the alkali-feldspat granites being a possible exeption.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-09-20T12:04:31Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Usma Cuervo 2016_Dissertação Mestrado Geociências UFPE.pdf: 11366215 bytes, checksum: ea3d3e75aa36f118697420651fd55f20 (MD5)<br>Made available in DSpace on 2016-09-20T12:04:31Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Usma Cuervo 2016_Dissertação Mestrado Geociências UFPE.pdf: 11366215 bytes, checksum: ea3d3e75aa36f118697420651fd55f20 (MD5) Previous issue date: 2016-02-22<br>FACEPE<br>Ao nordeste de São Jose de Belmonte, Pernambuco, o Complexo Riacho Gravatá Meso- a Neoproterozoico e o Grupo Cachoeirinha Neoproterozoico afloram. Ambas unidades de origem sedimentar e com intercalações de carbonato (mármore), formações de ferro bandado (BIF) e metavulcânicas são limitadas pela Zona de Cisalhamento Serra do Caboblo com direção NE. Outra importante caraterística da região é a abundante ocorrência de plutons graníticos criogenianosediacaranos que intruem o Grupo Cachoeirinha. O Complexo Riacho Gravatá com maior contribuição de material vulcânico, registra um evento extensional de formação de bacias relacionado com uma zona próxima de magmatismo de arco. O Grupo Cachoeirinha corresponde a uma sequência metaturbidítica, é dividido em Formação Santana dos Garrotes (unidade basal) e Formação Serra Olho d’Água (unidade superior) depositado numa bacia de retro arco. Quimioestratigrafia elemental e isotópica de seções selecionadas foi realizada objetivando estabelecer condições deposicionais de formação de carbonatos e formações ferríferas e estimar sua cronologia. Petrologia de plutons graníticos teve a intenção de elucidar ambiente tectônico e condições de cristalização destes corpos. A seção Barro do Complexo Riacho Gravatá é composto principalmente de mármores dolomíticos. A composição isotópica destes carbonatos com δ13C de -2,8 a -0,7‰ e δ18O de -15.0 a -15.8‰ podem ser correlatos com seções de final do Esteniano a inicio do Toniano. Os padrões de ETRY permitem inferir um ambiente deposicional marinho sob condições anóxicas e contribuição de fluidos hidrotermais. Da Formação Santana dos Garrotes, mármores calcíticos das localidades de Pedreira e Oiti mostram δ13C médios de +4,9‰ e +4,1‰, respectivamente, além de anomalias negativa de Ce e positiva de Y, sugerindo uma idade de deposição Criogeniano médio a tardio num ambiente levemente oxigenado. Os padrões de ETRY normalizados em relação ao PAAS para o BIF da Localidade Oiti são a favor de uma precipitação hidrogenética com influência hidrotermal. Química em rocha total e mineralde plutons granodioriticos com epidoto magmático ao norte do povoado Carmo permitem identifica-los como cálcio-alcalino principalmente, e cálcio-alcalinos de alto K, de origem mista. Estes granodioritos provavelmente forma intruidos durante a fase final de um regime de subdução, cristalizando sob pressões de 6,6 – 9,3 kbar e temperaturas entre 720 e 765°C, a uma profundidade ao redor de 22 Km.<br>To the northeast of the São Jose de Belmonte, Pernambuco, the Meso- to Neoproterozoic Riacho Gravatá Complex and the Neoproterozoic Cachoeirinha Group outcrops. Both units of sedimentary origin and with carbonate (marble), banded iron formation (BIF) and metavolcanic intercalations are limited by the Serra do Caboclo Shear Zone with a NE direction. Another important characteristic of the area is the abundant occurrence of Cryogenian-Ediacaran granitic plutons that intrude the Cachoeirinha Group. The Riacho Gravatá Complex with great contribution of volcanic material, record an extensional event of basin formation related to a nearby zone of arc magmatism. The Cachoeirinha Group corresponds to a metaturbiditic sequence, it is divided into the Santana dos Garrotes Formation (basal unit) and the Serra Olho d’Água Formation (upper unit) deposited in a back-arc basin. Elemental and isotope chemostratigraphy of selected sections was carried out aiming at precising the depositional conditions of carbonate and iron-bearing sediment formation and estimating their chronology. Petrology of granitic plutons had the intention of elucidate tectonic environment and crystallizing conditions of these bodies. The Barro section of Riacho Gravatá Complex is composed mainly of dolomitic marbles. The isotopic composition of these carbonates with δ13C varying from -2.8 to -0.7‰ and δ18O from -15.0 to -15.8‰ can be correlated with late Stenian – early Tonian sections. The REE+Y patterns led to infer a marine depositional environment under slightly anoxic conditions and hydrothermal fluids contribution. From Santana dos Garrotes Formation, calcitic marbles at the Pedreira and Oiti localities display average δ13C, respectively, of +4.9‰ and +4.1‰, besides negative Ce anomaly and positive Y anomaly, suggesting a middle to late Cryogenian depositional age in a slightly oxygenated environment. The PAAS normalized REE + Y patterns for BIFs at the Oiti locality favor a hydrogenetic precipitation with hydrothermal influence. Bulk and mineral phase chemistry analyses of magmatic epidote-bearing granodioritic plutons to the north of the Carmo village allow identify them as calc-alkalic and high K calc-alkalic, of mixed origin. These granodiorites were likely intruded during final stages of a subduction regime, crystallizing under pressures of 6.6–9.3 kbar and temperatures in the 720–765°C range, at depths around 22 Km.

Η παρούσα έρευνα αναφέρεται στην πετρολογική και κοιτασματολογική μελέτη του πλουτωνίτη της νήσου Τήνου και την συνδεδεμένη μ' αυτόν μεταλλοφορία σεελίτη (βολφραμιούχος) τύπου skarn. Ο ασβεσταλκαλικού χαρακτήρα πλουτωνίτης δείχνει τεκτονικού-θερμομεταφορικού τύπου επαφή με τα πετρώματα του πλαισίου. Συνίσταται άπό δύο βασικές λιθολογικές φάσεις: έναν μεταργιλικού χαρακτήρα βιοτιτικό-κεροστιλβικό γρανοδιορίτη που τοποθετήθηκε γύρω στους 17 Μα σε καθεστώς συμπίεσης σε θερμοκρασία ~770οC και πίεση ~5,2 Kbars. Ο γρανοδιορίτης προήλθε από ένα μάγμα που ήταν αποτέλεσμα μερικής τήξης υλικών μανδυακής προέλευσης και πετρωμάτων του ανώτερου φλοιού. Ο δεύτερος λιθότυπος πλουτωνίτη είναι ένας περιφερειακά αναπτυσσόμενος υπεραργιλικός γρανιτικός - βιοτιτικός λευκογρανίτης. Ο λευκογρανίτης τοποθετήθηκε γύρω στα 14 Μα σε καθεστώς διαστολής σε θερμοκρασία ~680οC και πίεση ~2Kbars. Κρυσταλλώθηκε από μάγμα που προήλθε από την μερική τήξη του γρανοδιορίτη και των περιβαλλόντων μεταϊζημάτων. Γύρω από τον πλουτωνίτη σχηματίσθηκε άλως επαφής πάχους ~1km. Μέσα στην ζώνη του πυροξενικού κερατίτη εντοπίστηκαν σε δύο περιοχές της δυτικής επαφής του πλουτωνίτη οι σχηματισμοί skarn πυροξένου - γρανάτη. Ο τύπος του skarn είναι "οξειδωτικός" εντούτοις διατηρούνται υπολέιμματα του αναγωγικού σταδίου (πλούσιοι σε εδεμβεργίτη πυρόξενοι και πλούσιοι σε γροσσουλάριο πυρήνες γρανατών που έχουν υποστεί ανθρακορρωγμάτωση). Η μεταλλοφορία του σεελίτη εντοπίστηκε μέσα στην ζώνη του πυροξενικού κερατίτη ως αποτέλεσμα διηθητικών - μετασωματικών διαδικασιών. Οι μεγακρύσταλλοί του βρίσκονται σε ισορροπία με τον υδροθερμικό γρανάτη (ζωνώδεις κρύσταλλοι πλούσιοι σε ανδραδίτη με παλμική ζώνωση και ανισοτροπία) και έχουν αποτεθεί σε θερμοκρασία ~375 οC (από ρευστά εγκλείσματα) και πίεση μικρότερη των 500 bars.<br>The present work is a petrological and mineralization study of the Tinos pluton and particularly of the tungsten skarn ie scheelite mineralization associated with this intrusion. the calcalkaline pluton displays a thermal - tectonic contact with the country rocks. It consists of two lithotypes: a metaluminous biotite- hornblende granodiorite and emplaced ca.17Ma under compression at T~700oC and P ~ 5.2kbars. The granodiorite represents a partial melt of mantle derived and upper crustal materials. The second lithotype of Tinos pluton is a peripherally occurring metaluminous garnet - biotite leucogranite that was emplaced ca. 14Ma at T ~ 680oC and P ~ 2kbars. The leucogranite crystallized from a magma representing a hybrid partial melt from the granodiorite and the encasing metasedimentary rocks. A contact halo of ~1km was formed around the Tinos pluton. In the pyroxene hornfels zone in the western part of the halo, mineralized pyroxene - garnet skarns were developed in two areas as a result of pyrometasomatism followed by infiltration metasomatism. The type of the Tinos skarn is "oxidized" however retains "reduced" characteristics such as hedenbergite and garnet rich in grossular component. The carbofractured grossular garnet cores with hourglass twinning are overgrown by anisotropic, oscillatory - zoned andradite - rich mantles. The scheelite megacrysts are in equilibrium with the latter, hydrothermal garnet. Fluid inclusion studies indicate that the scheelite has crystallized at T~375oC and pressure lesser than 500bars.

Granites constitute the main rock components of the Earth’s continental crust, which suggested to be formed in variable geodynamics environments. The different types of granitic rocks, their compositional characteristics, tectonic settings and magma sources are outlined. Mineralogical classification of granites includes four rock types: tonalites, granodiorites, granite (monzogranite and syenogranites) and alkali-feldspar granites. Alphabetical classification subdivided granites into: I-type, S-type, A-type and M-type granites. Moreover, formation of granitic magmas requires distinctive geodynamic settings such as: volcanic arc granite (Cordilleran); collision-related granites (leucogranites); intra-plate and ocean ridge granites. The Eastern Desert of Egypt (ED) forms the northern part of Nubian Shield. Both older and younger granites are widely exposed in the ED. Old granites (OG) comprise tonalites and granodiorites of syn- to late-orogenic granitoid assemblages. They are calcalkaline, I-type, metaluminous and display island arc tectonic setting. Younger granites (YG) on the other hand, include granites, alkali-feldspar granites and minor granodiorites. They are of I- and A-type granites and of post-orogenic to anorogenic tectonic settings. The majority of the YG are alkaline, A-type granite and of within-plate tectonic setting (WPG). The A-type granites are subdivided into: A2-type postorogenic granites and A1-type anorogenic granites. Granite magma genesis involves: (a) fractional crystallization of mafic mantle-derived magmas; (b) anatexis or assimilation of old, upper crustal rocks (c) re - melting of juvenile mafic mantle – derived rocks underplating the continental crust. Generally, older I-type granitoids were interpreted to result from melting of mafic crust and dated at approximately 760–650 Ma, whereas younger granites suggested to be formed as a result of partial melting of a juvenile Neoproterozoic mantle source. Moreover, they formed from anatectic melts of various crustal sources that emplaced between 600 and 475 Ma.