Petrology

Estudio paleoambiental a partir de precipitados químicos: espeleotemas de la Sala Roja (Cueva Goikoetxe, Busturia, Bizkaia)

by Virginia Martínez-Pillado

Paleoenvironmental study from chemical precipitates: Speleothems of the Sala Roja (Goikoetxe cave, Busturia, Bizkaia)

A microscopic information system (MIS) for petrographic analysis

by Simone Tarquini

Tarquini S., Favalli M.
2010, Computers & Geosciences 36, 665-674

The database and visualization facilities of Geographic Information System (GIS) software are employed to support the... more The database and visualization facilities of Geographic Information System (GIS) software are employed to support the analysis of rock texture from thin section by image processing. A Microscopic Information System (MIS) is hence obtained. The method is applied to transmitted light images of 137 samples obtained from 8 granitoid rocks. A slide scanner and a mount for crossed polarization are used to acquire the input images. For each thin section 5 collimated RGB images are scanned: 4 under different directions of crossed polarization and 1 without polarization. A grain segmentation procedure, based on two region growing functions is applied. The output is converted to vector format and refined using editing tools in the MIS environment, which enables a straightforward match between the input imagery and the final vectorized texture. GIS software provides optimal management of the MIS database, allowing the cumulative measurement of more than 87,000 grains.

Un ensemble lithique en calcédoine dendritique à Ath – Ferme de Tenre (prov. Hainaut, Belgique)

by Nick Van Liefferinge

Published in 'Quadriga'.

Is the Macroscopic Classification of Flint useful? A Petroarchaeological Analysis and Characterization of Flint Raw Materials from the Iberian Neolithic Mine of Casa Montero. 2009

by Teresa Orozco-Köhler

M.A. Bustillo; N. Castañeda; M. Capote; S. Consuegra; C. Criado; P. Diaz-del-Río; T. Orozco; J.L. Pérez-Jiménez & X. Terradas.
published in Archaeometry, 51 (2) 2009: 175-196.

Casa Montero is a mining complex located outside Madrid (Spain), dated from the Early Neolithic (c.5400–5000 calBC). An area of some 4 ha has been investigated and some 4000 shafts recorded, of which 324 have been excavated. The characterization of its raw flint materials and the establishment of its diagnostic features are indispensable in the reconstruction of the distribution of the mine’s products beyond the immediate site. This work reports the geological study of the mine’s Miocene flint layers and their petrological characterization. Archaeological samples from the mine’s shafts were classified according to macroscopic features and petrological characteristics.

Is the Macroscopic Classification of Flint Useful? A Petroachaeological Analysis and Characterization of Flint Raw Materials from the Iberian Neolithic Mine of Casa Montero

by Nuria Castañeda

BUSTILLO, M.A., CASTAÑEDA, N., CAPOTE, M., CONSUEGRA, S., CRIADO, C., DÍAZ-DEL-RÍO, P., OROZCO, T., PÉREZ-JIMÉNEZ, J.L., TERRADAS, X. 2009: Archaeometry, 51(2): 175-196.

Casa Montero is a mining complex located outside Madrid (Spain), dated from the Early Neolithic (c. 5400–5000 cal bc).... more Casa Montero is a mining complex located outside Madrid (Spain), dated from the Early Neolithic (c. 5400–5000 cal bc). An area of some 4 ha has been investigated and some 4000 shafts recorded, of which 324 have been excavated. The characterization of its raw flint materials and the establishment of its diagnostic features are indispensable in the reconstruction of the distribution of the mine's products beyond the immediate site. This work reports the geological study of the mine's Miocene flint layers and their petrological characterization. Archaeological samples from the mine's shafts were classified according to macroscopic features and petrological characteristics.

EL SÍLEX CASA MONTERO: ESTUDIO Y CARACTERIZACIÓN (2010)

by Nuria Castañeda

CRIADO, C., CASTAÑEDA, N., CAPOTE, M., BUSTILLO, MªA., PÉREZ-JIMÉNEZ, J.L., CONSUEGRA, S., DÍAZ-DEL-RÍO, P., OROZCO, T. y TERRADAS X. (2010): “El ‘sílex Casa Montero’: estudio y caracterización”. En S. Domínguez-Bella, J. Ramos Muñoz, J.M. Gutiérrez López y M. Pérez Rodríguez (eds.): Minerales y Rocas en las sociedades de la Prehistoria. Grupo de Investigación HUM-440. Univ. de Cádiz. Publicación Digital.

The aim of this paper is to present the characterisation of the siliceous rocks from the Neolithic mine of Casa... more The aim of this paper is to present the characterisation of the siliceous rocks from the Neolithic mine of Casa Montero (5400-5200 cal. BC). It is located in Madrid (Spain) and it occupies 4 hectares with 3897 mapped shafts, out of which 324 have been excavated throughout three field seasons.
This kind of study is essential in order to establish the diagnostic features of the raw material and to investigate the distribution of the mine’s products. An analysis of the relationship between different siliceous raw materials and the lithic operative chain has been carried out as well.
The characterisation has been performed using two methods: macroscopic description and petrological analysis. Seven macroscopic types (from 1 to 7) and four petrological groups (from A to D) have been established. The macroscopic classification has been found to be fundamental in the
analysis of the lithic remains, given the large volume of lithic material recovered in the site. The petrological classification provides a good method for identifying materials from the Casa Montero mine at other archaeological sites.
The observation of refits has suggested a preference for a certain raw material. In order to verify this, an statistical Factorial Analysis has been applied to study the representation of each phase of the lithic operative chain in each macroscopic type of raw material.

Discovery of green flint incorporated in quartzarenitic sandstone of early eocene age in the Belgian basin (Flobecq, Belgium)

by Nick Van Liefferinge

De Ceukelaire M & Van Liefferinge N.
Poster presented at GEO REG, forum de la fédération française des géosciences (Villeneuve d'Ascq, 23-27 octobre 2011)

A Petrographic Approach to Sand-tempered Pottery Provenance Studies: Examples from Two Hohokam Local Systems

by James Heidke

Co-authored with Elizabeth J. Miksa and Henry D. Wallace

Magma ascent along a major terrane boundary: crustal contamination and magma mixing at the Drumadoon Intrusive Complex, Isle of Arran, Scotland

by Valentin Troll

PETROGRAFÍA Y GEOQUÍMICA DEL BASAMENTO METAMÓRFICO AL SUR DEL LAGO ÑORQUINCO, PROVINCIA DE NEUQUÉN, ARGENTINA

by Ernesto Gallegos

GALLEGOS, E. 1,2, VATTUONE, M. E. 1 y OSTERA H. A. 2
1 Consejo Nacional de Investigaciones Científicas y Técnicas – Instituto de Geocronología y Geología Isotópica (INGEIS). E mail: ernesto@ingeis.uba.ar
2 Departamento de Ciencias Geológicas – Facultad de Ciencias Exactas y Naturales – Universidad de Buenos Aires.

ABSTRACT
The aim of this study is to characterize by means of petrography and geochemistry of metamorphic rocks... more ABSTRACT
The aim of this study is to characterize by means of petrography and geochemistry of metamorphic rocks that form the crystalline basement of the study area. A total of eight locations were identified. Petrographic traditional and detailed analysis was complete on each location. In five locations complete chemical analysis were conducted of bulk rock samples.
The analyzed rocks are petrographically divided into two groups characterized by different metamorphic mineralogy. These two groups represent their different protoliths, sedimentary and igneous (acid to intermediate). This supports the results of chemical analysis, which show main differences for SiO2, Al2O3, MgO, K2O, Sr and Rb abundances.
Key words: Formación Colohuincul – Geochemistry – Petrography – Petrology – Neuquén.
Palabras clave: Formación Colohuincul – Geoquímica – Petrografía – Petrología – Neuquén.

PETROLOGÍA PRELIMINAR DE LA GRANODIORITA PASO DE ICALMA EN EL VALLE DEL RÍO PULMARÍ, NEUQUÉN

by Ernesto Gallegos

GALLEGOS, E. 1,2, VATTUONE, M. E. 1 y OSTERA H. A. 2
1 Consejo Nacional de Investigaciones Científicas y Técnicas – Instituto de Geocronología y Geología Isotópica (INGEIS). E mail ernesto@ingeis.uba.ar
2 Departamento de Ciencias Geológicas – Facultad de Ciencias Exactas y Naturales – Universidad de Buenos Aires.

ABSTRACT
The study of the basement, both igneous and metamorphic, of the study area, located in the Northern... more ABSTRACT
The study of the basement, both igneous and metamorphic, of the study area, located in the Northern Patagonian Andes, has been the subject of a debate during the last decades. This is given by the paucity and complexity of the outcrops. This paper aims to contribute to the knowledge of a region petrological relegated. To this end, work objectives raised as petrographic and geochemical characterization of the area studied, with the certainty that this information will form new evidence about the origin of the rocks that were found therein.
The study area consists mainly of metamorphic rocks of Paleozoic and Mesozoic granitoids. The country rock of the granitoids in the study area is given by the metamorphic rocks of Colohuincul Formation. Petrographic analysis, together with geochemical information can be interpreted that these rocks are part of a co-magmatic series, with limited variability across the area studied. In this sense arises from the geochemical analysis, it is rocks formed as part of the roots of the Cretaceous volcanic arc. Where there is a lower percentage of silica and the sample is classified as diorite on the TAS diagram, and may be a slightly more basic pulse of magmatism in the area for the formation period of the batholith (Cretaceous).
Key words: Granodiorita Paso de Icalma – Geochemistry – Petrography – Petrology – Neuquén.
Palabras clave: Granodiorita Paso de Icalma – Geoquímica – Petrografía – Petrología – Neuquén.

It All Comes Out in the Wash: Actualistic Petrofacies Modeling of Temper Provenance, Tonto Basin, Arizona, USA

by James Heidke

Co-authored with Elizabeth J. Miksa

Correspondence and Discriminant Analyses of Sand and Sand Temper Compositions, Tonto Basin, Arizona

by James Heidke

Co-authored with Elizabeth J. Miksa

Een ontsluiting van silex en opaal (‘Les Planchettes-vuursteen’) in de glauconiethoudende zanden van het Onder-Eoceen (Formatie van Gentbrugge, Lid van Pittem, België)

by Nick Van Liefferinge

Published in 'Nautilus-Info', 2011

The basal tectonic mélange of the Cabo Ortegal Complex (NW Iberian Massif): a key unit in the suture of Pangea

by Ruben Diez Fernandez

Journal of Iberian Geology, 2009
Arenas, R., Sánchez Martínez, S., Castiñeiras, P., Jeffries, T.E., Díez Fernández, R. and Andonaegui, P.

Recent field work and mapping in the lower units of the Cabo Ortegal Complex provided new data about the tectonic... more Recent field work and mapping in the lower units of the Cabo Ortegal Complex provided new data about the tectonic melange that appears in the lowest structural position: the Somozas Melange. This melange unit with average thickness of 1800 m is restricted to the eastern part of the complex, and is located at the advancing front of the allochthonous complexes of NW Iberia. Three rock units are involved in the melange: 1) an ophiolitic melange consisting of igneous rocks mixed with serpentinites; 2) a metasedimentary unit with phyllites and phyllonites, with scarce conglomerates, marbles and quartzites; 3) high-T metamorphic rocks with varied types of amphibolites and orthogneisses.|Two granitic rocks within the ophiolitic melange were dated using U-Pb zircon geochronology at 527 +/- 2 Ma and 499 +/- 1 Ma. Two different series of igneous rocks can be distinguished in this melange. The first series consists of gabbros, diorites, granitoids and basalts-basaltic andesites with calc-alkaline affinities. The second series contains common basaltic rocks, diabasic dikes and gabbros with chemical compositions typical of island-arc tholeiites. Both igneous series shared a common geographic setting, but the island-arc tholeiites are younger than the calc-alkaline igneous rocks. The two igneous series were probably generated in a mature volcanic arc located along the periphery of Gondwana. In the metasedimentary unit, a conglomerate from a large tectonic block included in serpentinites yielded age populations of detrital zircons suggesting that the sediments were deposited along the periphery of the West-African Craton. This conglomerate contains a large number of zircons (n = 24) with ages ranging 630-464 Ma, probably representing the chronology of the Pan-African event, including the magmatic activity in the volcanic arc where the igneous lithologies involved in the melange were generated. The maximum age of sedimentation for this conglomerate is estimated as latest Cambrian - earliest Ordovician, and constraints the end of the magmatic activity in the volcanic-arc. Within the unit of high-T rocks, an orthogneiss yields a U-Pb protolith age of 485 +/- 6 Ma, which is similar to other ages of igneous rocks in the basal allochthonous terrane in NW Iberia. The three rock assemblages forming part of the Somozas Melange may be linked to the evolution of a mature peri-Gondwanan volcanic arc. This volcanic arc was affected by pronounced extension which caused the opening of intra-arc basins, culminating the rifting and subsequent drift of the external parts of the arc during the opening of the Rheic Ocean. This opening started during a time interval constrained by the peak activity in a mature volcanic arc (c. 527-499 Ma) and the generation of intra-arc basins around the Cambrian-Ordovician boundary.|Tectonic melanges including high-P rocks have been classically related to subduction zone environments. Regional relationships in NW Iberia and the nature of the rock units involved in the Somozas Melange, suggest that two different subduction zones generated during oblique convergence and collision between Gondwana and Laurussia were active during the final stages of the assembly of Pangea. The first related to the underthrusting beneath Laurussia of the most external Gondwana margin (c. 370 Ma). The second subduction zone was a new one which accreted later remnants of a peri-Gondwanan arc and sediments of the continental margin below a layer of exhumed high pressure rocks. This oblique collision finished the closure of the Rheic Ocean and contributes to define the new oceanic domain located to the East of Pangea, the Palaeotethys.

Iberian late-Variscan granitoids: Some considerations on crustal sources and the significance of “mantle extraction ages”

by Daniel Pastor Galán

Magma ascent along a major terrane boundary: crustal contamination and magma mixing at the Drumadoon Intrusive Complex, Isle of Arran, Scotland.

by Fiona Meade

Meade, F.C., Chew, D.M., Troll, V.R., Ellam, R.M., Page, L.M. (2009). Magma ascent along a major terrane boundary: crustal contamination and magma mixing at the Drumadoon Intrusive Complex, Isle of Arran, Scotland. Journal of Petrology., v.50 (12), 2345-2374. http://petrology.oxfordjournals.org/content/50/12/2345

The composite intrusions of Drumadoon and An Cumhann crop out on the SE coast of the Isle of Arran, Scotland and form... more The composite intrusions of Drumadoon and An Cumhann crop out on the SE coast of the Isle of Arran, Scotland and form part of the larger British and Irish Palaeogene Igneous Province, a subset of the North Atlantic Igneous Province. The intrusions (shallow-level dykes and sills) comprise a central quartz–feldspar-phyric rhyolite flanked by xenocryst-bearing basaltic andesite, with an intermediate zone of dark quartz–feldspar-phyric dacite. New geochemical data provide information on the evolution of the component magmas and their relationships with each other, as well as their interaction with the crust through which they travelled. During shallow-crustal emplacement, the end-member magmas mixed. Isotopic evidence shows that both magmas were contaminated by the crust prior to mixing; the basaltic andesite magma preserves some evidence of contamination within the lower crust, whereas the rhyolite mainly records upper-crustal contamination. The Highland Boundary Fault divides Arran into two distinct terranes, the Neoproterozoic to Early Palaeozoic Grampian Terrane to the north and the Palaeozoic Midland Valley Terrane to the south. The Drumadoon Complex lies within the Midland Valley Terrane but its isotopic signatures indicate almost exclusive involvement of Grampian Terrane crust. Therefore, although the magmas originated at depth on the northern side of the Highland Boundary Fault, they have crossed this boundary during their evolution, probably just prior to emplacement.

A new caldera fault segment exposed at Slieve Gullion: implications for the emplacement of the early ring-complex.

by Fiona Meade

Troll, V.R., Meade, F.C., Chew, D.M., Emeleus, C.H. (2008). A new caldera fault segment exposed at Slieve Gullion: implications for the emplacement of the early ring-complex. Irish Journal of Earth Sciences, v. 26, pp 1-16.

A contact zone between porphyritic microgranite of the early ring-complex of the Paleocene Slieve Gullion igneous... more A contact zone between porphyritic microgranite of the early ring-complex of the Paleocene Slieve Gullion igneous centre and Lower Palaeozoic metasedimentary rocks of the Longford–
Down inlier was exposed along a 300m section excavated during construction of the new M1 motorway. The outcrop displays a thin sliver of Longford–Down metasediment in contact with porphyritic microgranite in a steep, and locally intensely crushed, contact zone that dips away from the ring-complex. This outcrop pattern is reminiscent of a ‘caldera-superfault’. Given the recent discussion on sheet versus ring-dyke emplacement of the early ring-complex at Slieve
Gullion, this new evidence argues in favour of the traditional ring-dyke model with magma ascending along an active ring fracture associated with caldera subsidence.