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En el sector centro-norte de la Sierra de Comechingones, el basamento igneo-metamorfico se encuentra dominado por un conjuntode rocas migmaticas que presentan diversos grados de fusion parcial y relaciones de fundido/residuo que se... more
En el sector centro-norte de la Sierra de Comechingones, el basamento igneo-metamorfico se encuentra dominado por un conjuntode rocas migmaticas que presentan diversos grados de fusion parcial y relaciones de fundido/residuo que se encuentran vinculadasprincipalmente a procesos de extraccion/acumulacion de fundidos y, en menor medida, a variaciones en el protolito. Las rocas masabundantes son metatexitas que, a escala de afloramiento y de modo transicional, gradan a cuerpos diatexiticos. Las relaciones decampo, la petrografia y la quimica de los elementos mayoritarios en roca total indican que derivarian de una secuencia metasedimentaria,cuyos protolitos se caracterizaban por la alternancia de sedimentos grauvaquicos-peliticos y grauvaquicos-psamiticos quealcanzaron las condiciones de fusion parcial durante la orogenia Pampeana (570-520 Ma). La consistencia en las estimaciones delas condiciones P-T, a partir del equilibrio de multirreacciones metamorficas de intercambio y transferencia neta combinadas conmultiequilibrios entre fases minerales, sugieren que la evolucion metamorfica estuvo marcada por un aumento progresivo del gradometamorfico entre los 600 °C y 850 °C a 0,7-0,8 GPa.
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Research Interests: Geology, Geochemistry, Geophysics, Seismology, Magma, and 7 moreRhyolite, Plagioclase, Volcanic Rock, Feldspar, Andesite, Batholith, and felsic
Fil: Nullo, Francisco E. Ministerio de Planificación Federal, Inversión Pública y Servicios. Secretaría de Minería. Servicio Geológico Minero Argentino (SEGEMAR); Argentina.Fil: Blasco, Graciela. Ministerio de Planificación Federal,... more
Fil: Nullo, Francisco E. Ministerio de Planificación Federal, Inversión Pública y Servicios. Secretaría de Minería. Servicio Geológico Minero Argentino (SEGEMAR); Argentina.Fil: Blasco, Graciela. Ministerio de Planificación Federal, Inversión Pública y Servicios. Secretaría de Minería. Servicio Geológico Minero Argentino (SEGEMAR); Argentina.Fil: Risso, Corina. Ministerio de Planificación Federal, Inversión Pública y Servicios. Secretaría de Minería. Servicio Geológico Minero Argentino (SEGEMAR); Argentina.Fil: Combina, Ana. Ministerio de Planificación Federal, Inversión Pública y Servicios. Secretaría de Minería. Servicio Geológico Minero Argentino (SEGEMAR); Argentina.Fil: Otamendi, Juan. Ministerio de Planificación Federal, Inversión Pública y Servicios. Secretaría de Minería. Servicio Geológico Minero Argentino (SEGEMAR); Argentina.La Hoja 5172-I y 5175-II, El Calafate, a escala 1:250.000, está situada en el extremo sur cordillerano de la provincia de Santa Cruz. La localidad má...
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Within the northern Famatina system, the Sierras Narvaez and Las Planchadas expose an almost complete series of plutonic, volcanic-subvolcanic, and sedimentary rocks. On the basis of petrologic, stratigraphic, and geochemistry... more
Within the northern Famatina system, the Sierras Narvaez and Las Planchadas expose an almost complete series of plutonic, volcanic-subvolcanic, and sedimentary rocks. On the basis of petrologic, stratigraphic, and geochemistry characteristics are distinguished three lithostratigraphic units, which according to previous studies are named Narvaez Formation, Suri Formation including two members I-Vuelta de las Tolas, II-Loma del Kilometro/Punta Petrea), and Las Planchadas Formation with two members I-Pastos Largos, and II-Punta Colorada. The detailed geological mapping and the examination of the geological relationships among the three lithostratigraphic units allow defining a high rank entity in the northern Famatina system named Chaschuil Group. The Narvaez Formation (482-485 Ma) corresponds to the first stages of the Famatinian magmatic arc between latitudes 27° and 28° South. The later development of peri-volcanic basins filled by volcanogenic apron and shelf volcano-sedimentary de...
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En la porcion norte de la sierra de Valle Fertil, aflora un conjunto de rocas anatecticas formadas por procesos de fusion parcial en facies de granulita. El analisis de elementos mayoritarios y traza, y su comparacion con los probables... more
En la porcion norte de la sierra de Valle Fertil, aflora un conjunto de rocas anatecticas formadas por procesos de fusion parcial en facies de granulita. El analisis de elementos mayoritarios y traza, y su comparacion con los probables protolitos y con resultados experimentales, sugiere que la variedad litologica encontrada esta fuertemente controlada por el avance de la fusion parcial asociada a la separacion efectiva del fundido en los niveles medios a profundos del arco magmatico Famatiniano. Aunque metatexitas y diatexitas contienen proporciones variables de fundidos, las metatexitas volumetricamente dominantes presentan composiciones similares a las de sus probables precursores, sugiriendo que, en gran medida, los fundidos anatecticos no habrian sido segregados de su fuente metasedimentaria. La composicion de los leucosomas en las metatexitas varia desde fundidos primarios a diferenciados; indicando sus caracteristicas geoquimicas que el rango composicional observado puede ser ...
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La Formacion Chuschin constituye una secuencia volcano-sedimentarias presente en el sector sur-occidental del Sistema de Famatina, asociada al arco magmatico desarrollado en el borde occidental de Gondwana durante el Ordovicico inferior y... more
La Formacion Chuschin constituye una secuencia volcano-sedimentarias presente en el sector sur-occidental del Sistema de Famatina, asociada al arco magmatico desarrollado en el borde occidental de Gondwana durante el Ordovicico inferior y medio. El analisis de facies realizado para esta Formacion, ha permitido caracterizar los depositos y definir algunas de las caracteristicas del vulcanismo y sedimentacion vinculado con la evolucion del arco famatiniano. En el area de trabajo han sido definidas, para la Formacion Chuschin, facies volcanicas coherentes, tales como riodacita masiva, riolita bandeada y riolita masiva con textura esferulitica. Otro tipo de facies interpretadas corresponde a las del tipo volcaniclasticas, ya sean autoclasticas, piroclasticas y volcaniclasticas resedimentados. Entre este tipo de facies se han descripto brecha hialoclastica; ignimbrita soldada; vitrofiro; brechas monomictica masiva; brecha polimictica masiva y arenisca tobacea. Ademas en el area se difere...
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El presente trabajo expone una síntesis de la geología que comprende al complejo cristalino que constituye la Sierra de La Aguada, provincia de San Luis, Argentina, desde un enfoque basado en las relaciones de campo, los rasgos... more
El presente trabajo expone una síntesis de la geología que comprende al complejo cristalino que constituye la Sierra de La Aguada, provincia de San Luis, Argentina, desde un enfoque basado en las relaciones de campo, los rasgos petrológico-estructurales y las características geoquímicas. Dicha serranía expone un basamento dominado por rocas plutónicas intermedias-máficas de afinidad calcoalcalina y granitoides félsicos peraluminosos, en conjunto intruidas en metamorfitas de bajo a medio grado metamórfico estabilizadas en condiciones de facies de anfibolita. Todo el conjunto litológico ha sido agrupado dentro del denominado complejo El Carrizal-La Aguada. El análisis de las relaciones de campo, la petrografía y la comparación de las características geoquímicas de las rocas plutónicas del área estudiada y aquellas pertenecientes a la suite ordovícica Famatiniana expuestas en la Sierra Grande de San Luis, sugiere una posible relación genética-temporal vinculada al desarrollo del arco m...
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La geologia de la sierra de Chavez esta constituida por rocas igneas y metamorficas intercaladas complejamente a todas las escalas, y corresponderian a la unidad mafica definida en la sierra de Valle Fertil. Cinco asociaciones litologicas... more
La geologia de la sierra de Chavez esta constituida por rocas igneas y metamorficas intercaladas complejamente a todas las escalas, y corresponderian a la unidad mafica definida en la sierra de Valle Fertil. Cinco asociaciones litologicas han sido identificadas en este complejo: dioritica, gabrica, metasedimentaria, milonitica y granitica-pegmatitica. Las estimaciones termobarometricas realizadas en las migmatitas indican condiciones de equilibrio para el pico metamorfico (M 1 ) de 876 °C y 8,3 kbar y reflejarian el efecto del magmatismo durante el Ordovicico Temprano (489 - 470 Ma). Las presiones aqui estimadas corresponden a las mayores paleo-profundidades reconocidas en todo el arco magmatico Famatiniano. Las relaciones de campo y el analisis estructural permitieron establecer la presencia de varias fabricas magmaticas y tectonicas, las cuales son: i) estructuras magmaticas (S 0 ) interpretadas como una foliacion magmatica primaria, ii) foliacion submagmatica a subsolida de alta temperatura y foliacion metamorfica (S 1 ), iii) foliacion milonitica estabilizada en facies de anfibolita (S 2a ) y esquistos verdes (S 2b ) y iv) foliacion fragil (S 3 ) definida como un clivaje de fractura centimetrico. (S 0 ) y (S 1 ) estan asociadas al primer estadio de deformacion (D 1 ) reconocido en la zona, desarrollado en condiciones de alta temperatura (facies de granulita) y coetaneo con el magmatismo y el pico metamorfico (M 1 ). (S 2a,b ) y (S 3 ) transponen a las estructuras igneas y metamorficas generadas durante el evento D 1 , y se asocian a un segundo y tercer estadio de deformacion (D 2- D 3 ), representando una evolucion progresiva de la deformacion desde dominios ductiles a fragiles, vinculadas a las etapas de cierre y exhumacion del arco Famatiniano.
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This work presents field relationships, petrography and structural features of the crystalline complex that form the central-western portion of the Valle Fértil range, San Juan. The crystalline complex comprises five main lithologic... more
This work presents field relationships, petrography and structural features of the crystalline complex that form the central-western portion of the Valle Fértil range, San Juan. The crystalline complex comprises five main lithologic associations: gabbroic rocks, dioritic rocks, metasedimentary migmatites, pegmatitic granites and mylonite series rocks. The fabric igneous preserved in the gabbroic association is which manifest as either layering of cumulate origin (S0a) and magmatic flow bands (S0b). In most places, the primary fabrics occur reworked and/or cross-cut by the submagmatic foliation (S1). However, S1 is associated with low differential stress and the only changes in the primary igneous and metamorphic mineral assemblages are growth of hornblende in mafic rocks and biotite + sillimanite in the metasedimentary rocks. This suggests that (D1) deformation acted under high temperature and synchronously with the igneous activity. Subsequent deformation (D2) is related to high-st...
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... Suya Taco and Sol de Mayo mafic complexes from eastern Sierras Pampeanas, Argentina: Evidence for the emplacement of primitive OIB-like magmas into deep crustal levels at a late stage of the Pampean orogeny. ...
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RESUMEN. Se describe por primera vez la petrografía y geoquímica de unidades volcánicas terciarias del sur de la provincia de Mendoza. Se analizan la nomenclatura estratigráfica y sus edades, estableciéndose una secuencia de eventos... more
RESUMEN. Se describe por primera vez la petrografía y geoquímica de unidades volcánicas terciarias del sur de la provincia de Mendoza. Se analizan la nomenclatura estratigráfica y sus edades, estableciéndose una secuencia de eventos magmáticos ...
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ABSTRACT New understanding of the mechanisms and rates by which magmatic arcs are constructed requires geological control from crustal cross-sections. Previously characterized arc sections are generally from island arcs, and may reflect... more
ABSTRACT New understanding of the mechanisms and rates by which magmatic arcs are constructed requires geological control from crustal cross-sections. Previously characterized arc sections are generally from island arcs, and may reflect relatively low-flux conditions potentially quite different than those associated with the large scale volcanism and rapid formation of pluton-flooded, mid-to-upper crust such as occurs in the Puna-Altiplano region today. However the deepest levels of the early Ordovician Famatinian arc crust provides a window into the 'plumbing' of a continental arc in flare-up mode and is exposed in an approximately 140 km by 40 km cross-section in the Sierras Valle Fertil-La Huerta in northwestern Argentina. The Valle Fertil portion of the arc grades continuously from regional-scale calc-alkaline metaluminous I-type granitoids (granodiorite into deeper heterogeneous tonalities) downward into a complex arrangement of large mafic intrusions (both cumulate and non-cumulate) and partially melted supracrustal packages composed largely of siliciclastic sediments. The region is characterized by granulite grade conditions formed broadly synchronously with igneous plutonic activity spanning up to 20 Ma, with a portion of the section recording 5.2-7.1 kbar and temperatures of 770-840°C. Peak metamorphic conditions produced thermal gradients of around 36° per km and there was little pressure change upon cooling producing a very flat ccw P-T loop. No resolvable differences in peak metamorphic conditions from localities along strike 70 km apart were detected, indicating that the arc is exposed at the same paleo-depth and the average crustal thickness was more than 20-25 km. It has also been proposed that this orogen formed in a margin without continent-continent collision and hence no terrane accretion. Thus the lower crustal section exposed in the Sierras Valle Fertil-La Huerta may be an analog for the Cenozoic high plateau of the Central Andes. This is an especially attractive idea as the large mafic bodies and heterogeneous tonalities might be an analog for the attenuating mid-crustal low velocity layer imaged in Puna-Altiplano region today. Our presentation will present work in progress on our efforts to refine the regional architecture of this arc with a special emphasis on applications to continental arcs in flare- up mode.
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[Este proyecto se propone] Profundizar el estudio del Basamento Cristalino del sur de la Sierra de Comechingones en tematicas no abordadas en detalle hasta el momento: a) Caracterizacion geoquimica de los tipos litologicos aflorantes; b)... more
[Este proyecto se propone] Profundizar el estudio del Basamento Cristalino del sur de la Sierra de Comechingones en tematicas no abordadas en detalle hasta el momento: a) Caracterizacion geoquimica de los tipos litologicos aflorantes; b) Determinacion de las condiciones termobarometricas del metamorfismo. El mapa geologico-estructural de detalle obtenido en anteriores investigaciones servira como marco de referencia para desarrollar los objetivos aqui planteados. El estudio geoquimico en roca total, se complementara con la quimica mineral, determinada con la utilizacion de microsonda electronica. Integrando esta base de datos se pretende determinar la petrogenesis de cada una de las asociaciones litologicas de la region. Con el desarrollo de estas lineas de investigacion, sumado a los resultados alcanzados en anos anteriores por este equipo de trabajo, se intentara determinar un modelo de evolucion geologico, tectonotermico, de los dos terrenos definidos para el sur de la sierra de Comechingones. Ademas del aporte al conocimiento geologico basico de las Sierras de Cordoba en particular y Pampeanas en general, el progreso y los resultados de la investigacion propuesta contribuiran a facilitar futuras tareas de evaluacion de los recursos minerales no-renovables en este sector de las Sierras Pampeanas. Objetivos generales Incrementar el conocimiento del Basamento Cristalino en este sector, profundizando en tematicas que aun no han sido investigadas detalladamente, complementado la geoquimica con la quimica mineral, determinada esta ultima con la utilizacion de microsonda electronica. Objetivos Especificos 1) Realizar la caracterizacion geoquimica de los tipos litologicos que constituyen el basamento del sur de la Sierra de Comechingones. 2) Determinar las condiciones del metamorfismo en variedades litologicas donde sea posible definir la evolucion termica de la secuencia cortical investigada. 3) [Con] El desarrollo de ambas lineas investigativas, con la complementacion de los resultados ya alcanzados, se intentara determinar un modelo de evolucion geologico tectonico en los terrenos que conforman el sur de la Sierra de Comechingones.
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La Hoja Geologica 2566-09 (Nevado de Acay) se hizo a traves de la empresa Pena Colorada S.A., y no de manera directa por el Servicio Geologico Minero Argentino. No se tiene la filiacion precisa de los autores, y es posible que parte de la... more
La Hoja Geologica 2566-09 (Nevado de Acay) se hizo a traves de la empresa Pena Colorada S.A., y no de manera directa por el Servicio Geologico Minero Argentino. No se tiene la filiacion precisa de los autores, y es posible que parte de la informacion de este boletin pueda necesitar revisarse.
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This paper presents a synthesis of the complex geology of the Las Lajas Shear Zone (LLSZ) through a detailed petrological - structural approach, in order to establish its importance in the evolution of the Sierra de Comechingones... more
This paper presents a synthesis of the complex geology of the Las Lajas Shear Zone (LLSZ) through a detailed petrological - structural approach, in order to establish its importance in the evolution of the Sierra de Comechingones basement. The LLSZ is a very important geological discontinuity, that was mainly active during the Paleozoic times although is still active and related to the regional tectonic framework. This shear zone is 35 km long and 1.5 km wide, and their limits and geological characteristic suggest it was active through ductile to fragile domains, been actually related to the Las Lajas- Sampacho-Las Lagunas fault system. Detailed analysis of the lithology and its internal structures suggest, based on the intensity of reworking of the protoliths and the proportions of mylonitic rocks ( s.l .), that the deformation intensity in the shear zone increases from north to south. Detail study of the deformation fabrics and their related structures has demonstrated that LLSZ i...
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La Hoja Geologica 2566-15 (La Poma) se hizo a traves de la empresa Pena Colorada S.A., y no de manera directa por el Servicio Geologico Minero Argentino. No se tiene la filiacion precisa de los autores, y es posible que parte de la... more
La Hoja Geologica 2566-15 (La Poma) se hizo a traves de la empresa Pena Colorada S.A., y no de manera directa por el Servicio Geologico Minero Argentino. No se tiene la filiacion precisa de los autores, y es posible que parte de la informacion de este boletin pueda necesitar revisarse.
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Abstract Trace element abundances in constituent minerals from mafic and ultramafic rocks of a deep arc crustal section are studied to observe their abundance and distribution. Five cumulate rocks were selected from a sequence that... more
Abstract Trace element abundances in constituent minerals from mafic and ultramafic rocks of a deep arc crustal section are studied to observe their abundance and distribution. Five cumulate rocks were selected from a sequence that consists of pyroxene hornblende peridotite, olivine hornblende gabbronorite, pyroxene hornblende gabbronorite, hornblende gabbronorite, gabbro and anorthosite. Solid/liquid partition coefficients calculated with the equilibrium distribution model indicate that Cr, Ni, Co, Zn and V are highly compatible with an olivine-dominated mineral assemblage from the mafic and ultramafic cumulates. The compatibility of Ti and Sc would be dependent on the stability of clinopyroxene, amphibole and oxides in the magmatic system. With few exceptions, the other trace elements are incompatible with the minerals that form the cumulate. At most half the mass of Sr carried by a primitive arc magma could be stored in anorthite-rich plagioclase from the mafic cumulates. Magmatic amphibole fractionates Y, middle and heavy REE from other incompatible elements during crystal accumulation of mafic cumulates. In contrast, late magmatic to subsolidus amphibole has no effect on the differentiation of a primitive arc magma. In fact, the trace element variability of amphibole and clinopyroxene is easily related to different stages of magmatic evolution within the cumulate pile. The results presented here are helpful for modelling other cases of arc magma petrogenesis where the cumulate rocks with dominant mafic assemblages are not exposed.
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The geology of the Sierra the Chavéz is constituted by igneous and metamorphic rocks that appear complexly inter-layered at all scales, and belong to the mafic unit from defined in the Sierra de Valle Fértil. Five lithological... more
The geology of the Sierra the Chavéz is constituted by igneous and metamorphic rocks that appear complexly inter-layered at all scales, and belong to the mafic unit from defined in the Sierra de Valle Fértil. Five lithological associations have been identified in this complex, which are: dioritic, gabbroic, metasedimentary, mylonitic and granitic-pegmatitic. Thermobarometric estimates performed in metasedimentary migmatites yield peak (M1) metamorphic conditions of 876 °C and 8.3 Kbar, and are interpreted to reflect Early Ordovician magmatism (~ 489-470 Ma). Maximum estimated metamorphic pressures correspond to one of the deepest crustal paleo-depths found all over the Famatinian arc. Field observations and structural analyses allow recognizing the presence of several magmatic and tectonic fabrics, which are: i) magmatic layering (S0) interpreted as primary magmatic foliation, ii) sub-magmatic to sub-solid high temperature foliation and metamorphic foliation (S1), iii) mylonitic fol...
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Geology and petrology of mafic-ultramafic body from Las Juntas, Valle Fértil, San Juan.
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Infernal structure of the migmatites of the northern portion of the Sierra de Valle Fértil, San Juan.
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We report petrologic and geochemical features of anhydrous granulites from the eastern Sierras Pampeanas, Argentina. Aluminous Grt–Crd-bearing granulite is the most abundant rock type in the study region, and hosts intermediate Opx–Grt... more
We report petrologic and geochemical features of anhydrous granulites from the eastern Sierras Pampeanas, Argentina. Aluminous Grt–Crd-bearing granulite is the most abundant rock type in the study region, and hosts intermediate Opx–Grt bearing granulites as interlayered lenses. Both granulite types crystallized under similar P–T conditions of T=850–900 °C and P c. 7.5 kbar. The formation of Grt–Crd granulites by subsolidus
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Interaction between mafic magmas and crustal metamorphic rocks at mid-crustal levels causes modification of mafic magma composition by assimilation or reaction with crustal materials. This petrologic process is studied at the Suya Taco... more
Interaction between mafic magmas and crustal metamorphic rocks at mid-crustal levels causes modification of mafic magma composition by assimilation or reaction with crustal materials. This petrologic process is studied at the Suya Taco Complex where a suite of mafic magmas interacted with metamorphic rocks at 6.6±1 kbar. The Suya Taco Complex consists of close-spaced bodies of biotite-bearing gabbronorites. These magmas intruded into a supracrustal sequence consisting of amphibolite– to granulite–facies gneisses and migmatites. The peak-metamorphic mineral assemblage Bt+Qtz+Pl(An30)+Grt+Kfs±Crd±Sil of supracrustal rocks crystallised before igneous mafic magmatism. Interaction between mafic magmas and metamorphic rocks produces two major hybrid lithologies: diorites made up of Opx+Bt+Pl (An38–50)+Ilm±Cpx±Qtz; and garnet- and orthopyroxene-bearing rocks characterised by the coexistence of Bt+Pl (An30–45)+Grt+Opx+Qtz+Ilm±Spl±Kfs. The latter lithology may locally appear as a quartz-absent and high-aluminous mineral assemblage. The two hybrid rocks occur interlayered at the contact zone between igneous mafic rocks and high-grade gneisses. Individual layers range from centimeter to meter scales; moreover, dioritic and orthopyroxene- and garnet-bearing layers present a spectrum of mineral assemblages and mineral chemistry that spread among those that appear in igneous mafic and metamorphic rocks. The work shows that the changes of mineral assemblages and variations of mineral chemistry in the hybrid diorites and orthopyroxene- and garnet-bearing rocks are the result of interaction processes between mafic magmas and regional metamorphic rocks. Field relationships, petrographic features, mineral compositional changes and qualitative analyses of phase relations suggest that rocks formed by interaction between mafic magmas and metamorphic rocks results from: (1) assimilation of metamorphic rocks by mafic magmas at variable degrees and (2) ion diffusion among mineral assemblages of contrasting composition. The implication of these processes is that Ca is transferred from mafic magmas to metamorphic rocks, which forces the breakdown of garnet and quartz, and induces the crystallisation of plagioclase and orthopyroxene in the resulting hybrid rocks.
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This work presents the field setting, petrography, mineralogy and geochemistry of a gabbroic and peridotitic layered body that is lens-shaped and surrounded by gabbronorites, diorites, and metasedimentary migmatites. This body exposed at... more
This work presents the field setting, petrography, mineralogy and geochemistry of a gabbroic and peridotitic layered body that is lens-shaped and surrounded by gabbronorites, diorites, and metasedimentary migmatites. This body exposed at Jaboncillo Valley is one among ...