Petrology

Snowflakes and silicate mushes are two examples of the terrestrial regimes that may be characterized as partially solidified systems. Change of phase in clouds and magma chambers as well as in the earth's mantle and core introduces a variety of phenomena to challenge both the mathematical modeler and the experimentalist intent upon understanding the nature of such processes. Paralleling the efforts of researchers in the natural sciences, metallurgists and materials scientists have extensively investigated solidification in alloy melts to discover the controlling mechanisms for undesirable behavior such as melt segregation, freckling (Figure 1), and crystal dislocation. Unfortunately, most of the studies, whether in the geosciences or in material sciences, have focused on highly specialized problems with little or no attempt at generalizing the results or methods to other physical systems. During May 12-16, 1986, at the Stanford University Conference Center at Fallen Leaf Lake, ...

Experiments were performed from 1•0 to 8•5 GPa in a peralkaline INTRODUCTION system K 2 O-Na 2 O-CaO-MgO-Al 2 O 3-SiO 2-H 2 O (KNCMASH) K-rich amphiboles are exotic members of the amphibole to investigate the stability and composition of richteritic amphiboles family in terms of their frequency of occurrence at in the MARID (mica-amphibole-rutile-ilmenite-diopside) asthe Earth's surface. With few exceptions they are semblage amphibole + phlogopite + clinopyroxene. The results represented by K-rich varieties of richterite Nawere compared with phase relations and the composition of natural CaNaMg 5 Si 8 O 22 (OH) 2 , katophorite NaCaNaMg 4-MARIDs to assess possible mechanisms of formation for MARID-AlSi 7 AlO 22 (OH) 2 and, more rarely, arfvedsonite type rocks. K-richterite is stable in a wide range of bulk K/Na NaNa 2 Mg 4 Fe 3+ Si 8 O 22 (OH) 2. The vast majority of known ratios in the MARID assemblage to 8•5 GPa and 1300°C. In occurrences is confined to extremely alkaline, Kthis assemblage the amphibole can accommodate significant amounts dominated mainly magmatic environments which are of K on the M(4)-site and shows a systematic increase in the K/ poor in Al and partly Si undersaturated. Experimental Na ratio with increasing pressure. At P >7•0 GPa, K-richterite results on K-richterite stability show that this amphibole can coexist with garnet. Phase relations of K-richterite in a natural can act as a principal reservoir for alkalis and water MARID composition are consistent with those in the simplified as well as for a number of incompatible trace elements system and confirm the potential stability of K-richterite and Kin the Earth's mantle down to transition zone depths, richterite + garnet within the diamond stability field. The asand may be involved in deep-seated magma generation semblage K-richterite + phlogopite + clinopyroxene is incompletely processes: K-richterite (or Ti-and/or F-rich varieties) buffered in the KNCMASH system, resulting in a systematic relation is thought to be a source component of lamproites between bulk-and mineral compositions observed in the experiments. and group II kimberlites (orangeites) (Foley, 1992; Such a correlation, however, cannot be observed in natural MARIDs. Taylor et al., 1994; Mitchell, 1995b). Therefore, MARID-type rocks do not represent the bulk composition Previous studies have dealt with K-richterite stability from which they formed and, hence, must be products of an openin various bulk systems and little attention has been system crystallization. given so far to K-richterite chemistry as a function of P, T and bulk chemistry of the mantle. Thus, the aims of the present study are twofold: first, to assess the stability of K-richterite as a function of P and T in a peralkaline bulk composition; second, to consider the dependence of the chemistry of amphibole and coexisting clinopyroxene and phlogopite upon changing

U-series isotopes can provide unique insights into the physical processes of magma evolution by constraining the time scales over which they operate. This, however, requires rock suites that provide a clear and complete record of the liquid line of descent. Sangeang Api volcano, in the east Sunda arc, provides such an opportunity because it erupts potassic lavas (SiO 2 $ 47±55%), which contain a spectrum of xenoliths interpreted to represent the cumulates complementary to the lavas. Combined, the cumulates and lavas span a large compositional range, which major and trace element modelling suggests reflects $70% polybaric crystallization that began at sub-Moho depths and continued into the upper crust. The parental magmas can be successfully modelled by $3% dynamic partial melting, in the presence of 0±4% residual garnet, of a mid-ocean ridge basalt (MORB) source enriched by $3% subducted Sunda sediment in addition to a contribution of fluid-mobile elements from the subducting slab. The effects of fluid addition and partial melting on U±Th disequilibria appear to be competing processes. A moderate range in Sr, Nd and Pb isotopes is interpreted to reflect a combination of source heterogeneity and 515% assimilation of Indian MORB crust. Neither interaction with metasomatized arc lithosphere nor the presence of enriched, plume-type mantle in the mantle wedge is required by our data. The cumulates and lavas have largely indistinguishable ( 230 Th/ 232 Th) over a wide range of U/Th ratios and thus any age differences are minimal relative to the half-life of 230 Th. All whole rocks and minerals are characterized by 226 Ra excesses and modelling of the 226 Ra± 230 Th±Ba data suggests that magmatic evolution beneath this arc volcano occurs on time scales of $2000 years. Combining this with simple numerical calculations we estimate that the Sangeang Api magma chamber is $6±10 km 3 in size, cooling rates are $0Á05 C/yr and minimum crystal growth rates are (2±7) Â 10 À13 cm/s. It is possible that a significant proportion of the crystal growth and differentiation occurred during isobaric decompression of magmas ascending through conduits. An implication is that the net magmatic flux across the Moho is of magmas that are already significantly evolved from primary magmas and this may be significant for why average continental crust has an andesitic bulk composition even though the flux out of the mantle wedge is basaltic.

Copyright 2009, Society of Petroleum Engineers This paper was prepared for presentation at the 2009 SPE/EAGE Reservoir Characterization and Simulation Conference held in Abu Dhabi, UAE, 19–21 October 2009. This paper was selected for presentation by an SPE ...

Oriented lamellar inclusions of pyroxene and rutile in mantle garnet often serve as evidence for majoritic and titaniferous precursor garnets, respectively. We investigated ten new such microstructure-bearing samples from six orogenic peridotite bodies in SW Norway, which originated in the E Greenland mantle lithosphere, petrologically and thermobarometrically. All pyroxenite (nine) and eclogite (one) samples have large (mainly porphyroclastic) garnet containing silicate and oxide inclusions with shape-preferred orientation relationship. These inclusions vary—dependent on their size—systematically in shape (acicular to subprismatic), width (∼50 μm to submicron size), spacing (several 100 to ∼10 μm) and phase (pyroxene to Ti-oxide ± pyroxene). Smaller inclusions can fill the space between larger inclusions, which support the idea of consecutive generations. The larger, early formed lamellae occur least frequent and are most poorly preserved. A younger generation of other inclusions d...

The study of production techniques, typology and distribution of over 1000 Iron Age and Roman rotary handmills from Switzerland is related to the rescue excavation of the millstone quarry of Châbles-Les Saux in the Canton of Fribourg. Mills have been classified according to petrology into seven groups and plotted in space. Sources of origin are proposed for each group. This general study is meant to provide a reference base of Swiss handmills for timber more specific archaeological and geological studies.

A Viking Lander 1 image was modeled as mixtures of reflectance spectra of palagonite dust, gray andesitelike rock, and a coarse rocklike soil. The rocks are covered to varying degrees by dust but otherwise appear unweathered. Rocklike soil occurs as lag deposits in deflation zones around stones and on top of a drift and as a layer in a trench dug by the lander. This soil probably is derived from the rocks by wind abrasion and/or spallation. Dust is the major component of the soil and covers most of the surface. The dust is unrelated spectrally to the rock but is equivalent to the global-scale dust observed telescopically. A new method was developed to model a multispectral image as mixtures of end-member spectra and to compare image spectra directly with laboratory reference spectra. The method for the first time uses shade and secondary illumination effects as spectral end-members; thus the effects of topography and illumination on all scales can be isolated or removed. The image was calibrated absolutely from the laboratory spectra, in close agreement with direct calibrations. The method has broad applications to interpreting multispectral images, including satellite images.

Steiner finnes overalt, de er lett tilgjengelige for alle, og de fleste barn fyller lommene sine med dem. Derfor er stein et tema for barnehagene. Utfordringen er at få av de voksne har grunnleggende kunnskap om stein. Dette ønsket vi å finne en løsning på, og her er resultatet av forsøk~t. I barnehagen hvor forsøket ble gjennomført, hadde barna lenge lekt lavalek. Det var et godt utgangspunkt for å starte et tema om stein og fossiler i barnehagen.

The Sept Iles layered intrusion (Quebec, Canada; 564 Ma) is a large plutonic body with a diameter of 80 km and a thickness of 6 km made up from its base to top of a layered series with troctolite and gabbro, and an upper border series with anorthosite, capped by cupolas of A-type granite. Chilled margin compositions suggest a ferrobasaltic parental magma close to that of the Skaergaard intrusion, but much richer in iron and titanium. Samples from drill-cores and surface sampling of the 4·7 km thick layered series reveal a succession of massive troctolites and layered gabbros that contain 24 Fe^Ti oxide layers cm-to m-thick and many anorthositic autolithic blocks. The sequence of crystallization in the layered series is: plagioclase (An 72^34 ) and olivine (Fo 75^21 ) followed by magnetite and ilmenite, then Ca-rich pyroxene and finally apatite. An olivine gap is observed between Fo 66 and Fo 59 . The saturation of Fe^Ti oxides before Ca-rich pyroxene is interpreted to be the result of the high FeO t and TiO 2 contents and the low CaO content of the parental magma. Contamination by old continental crust has occurred during crystallization of the layered series, as indicated by Sr isotopic compositions ( 87 Sr/ 86 Sr 564 ¼ 0·70360^0·70497). The differentiation trend of the intrusion is interrupted by two large and many small reversals to more primitive compositions of cumulus phases, Cr content of magnetite and lower Sr isotope ratios. These reversals and the intermittent disappearance of some phases are interpreted as resulting from magma chamber replenishments by undifferentiated primitive basaltic magma and mixing with the resident magma.

Porosity is one of the most important characteristics for modeling reservoir. In recent years, some new methods for estimation have been introduced, which are more applicable and accurate than old methods. Fuzzy logic has shown reliable results in petroleum modeling area for describing reservoir characteristics. In this study, a Sugeno fuzzy model has been formulated to predict porosity. In order to select the number of membership function, subtractive clustering method was utilized through Gaussian membership functions. Another technique for predicting porosity was multiple linear regression to compare with fuzzy logic technique. Results indicated that correlation between real value from core data and the predicted value by fuzzy logic was more accurate than multiple linear regression technique in this scope.

In situ mineral (garnet, zircon) trace element and garnet^rock REE distribution data obtained on leucogranulites from the Bohemian Massif are consistent with an origin of these now strongly deformed rocks as migmatitic leucogranites formed through dehydration-melting of muscovite-bearing protoliths at high pressures during the Variscan orogeny. Partial melting at P^T conditions of 900^9408C and 1·6^1·8 GPa consumed mica and feldspar to produce peritectic kyanite and high-Ca (20^24 mol % grossular), high-Eu garnet along with leucogranitic melt. D REE (Grt/rock) values calculated from this garnet and its host rock are consistent with garnet^melt equilibrium at these P^T conditions. Ternary feldspar and rutile (2000^3200 ppm Zr) crystallized from the leucogranite melts in the migmatites at minimum temperatures of 4880^9208C. These formed along with apatite prior to and accompanying the crystallization of garnet rims and the majority of the garnet that occurs in the leucogranulites. This garnet is typified by strong depletion in Eu and D REE (Grt/rock) values consistent with garnet^melt equilibrium only after the fractionation of apatite (50·3 wt %) and ternary feldspar (5^15 wt %). Zircons in one leucogranulite are dominated by oscillatory-zoned grains that yield pre-Variscan U^Pb ages (495 and 433 Ma) and crystallized, from Ti-in-zircon thermometry, at 700^8108C in their original host magmas. These xenocrystic grains are potentially preserved because of the short timespan of the high P^T Variscan event at 340 Ma and the moderate amounts of leucogranitic partial melt present in the rocks, estimated as at least 30 wt % melt from Zr mass balance. The production of new zircon associated with the Variscan event in this leucogranulite is limited to weakly zoned zircon rims characterized by flat heavy REE patterns that approach REE equilibrium with garnet rims. This post-peak zircon was formed at minimum P^T conditions of 8408C and 0·8^1·0 GPa along the decompression-cooling path defined by previous work for the Bohemian Massif granulites. The garnetŵ hole-rock REE relationships, observation of Eu depletion between early and later garnet growth phases, and Zr^Ti thermometric estimates indicating temperatures of 48408C for this evolution cannot be explained by the alternative interpretation of the leucogranulites as reworked and recrystallized pre-Variscan low-P granitoids, but support a model in which the Bohemian leucogranulites were high-P Variscan-age migmatites containing significant amounts of melt.

In this paper we approach the study of a ceramic recipe based on the addition of crushed spathic calcite as temper. We first briefly discuss the anthropological significance underlying the identification of technological paste recipes, as well as the spatial distribution of the spathic calcite recipe in the Mediterranean basin. Subsequently, we focus on the possibilities of identifying this recipe using several analytical methods, including binocular microscopy, image analysis, petrology, X-ray powder diffraction and X-ray fluorescence. Thus, the complementarity existing between different methods commonly applied in pottery analysis is considered in order to know the potential of these various techniques to identify spathic calcite recipe and classify the ceramic record to maximize the social archaeological interpretation of the data. The final objective is to know the feasibility and limitations that certain analytical procedures - such as the binocular microscopy- have for extrapolating the identification of this recipe to a larger series of ceramics from only certain features of the paste.

Volcanoes are an important source of gases and aerosols in the atmosphere. Significant quantities of trace elements are emitted as vapor species [Nriagu, 1989; Symonds et al., 1987] and are strongly enriched in the gas relative to the magma [Tazieff and Sabroux, 1983; Crowe et al., 1987]. After eruption the trace elements condense on ash and other particles or they form sublimates and agglomerates. Here we report on the emission of gold (Au) from Mount Erebus, Antarctica. Although the flux of emitted Au is low compared to other volcanoes, crystalline particulate Au has been found in the plume near the crater, in ambient air up to 1000 km from the volcano and in near surface samples. Vapor phase transport of Au may occur as a chloride species and could be an important transport mechanism in crystallizing magmatic intrusions.

Computerized evaluation of Vibroseis similarity test data is the logical consequence of the increasing quality requirements for signal reproducibility and for synchronization of vibrators. The differences in start time and phase as well as an indication of local phasing problems between any two Vibroseis signals can be obtained from an analysis of the difference of their respective phase spectra. This method appears to be accurate and stable with respect to harmonics which usually plague the signals from transducers monitoring the motion of the vibrators'base plates.

The probability of the occurrence of porphyry copper ore associated with subduction zone of the Neo-Tethys ocean and volcanic arc of Iran (Urumieh-Dokhtar) justifies the necessity of exploration and prospection of this type of ore in Iran. Zafarghand index and Kahang deposit of porphyry copper-molybdenum located in Isfahan province, center of Iran using Satellite data interpretations were discovered in the years of 2010 and 2003, respectively. Geological studies have indicated the presence of argillic and propylitic alteration halos associated with porphyry copper systems. The 250 rock samples were systematically collected at a sampling distance of 100 m and in the center of the porphyry system by a distance o f 50 m in Zafarghand. Also, 377 samples of lithogeochemicals (185 rock samples and 192 soil samples) were extracted systematically from Kahang deposit. The study of geochemical data of rock and soil samples showed similarity of these two types of mineralization with other mineralization of porphyry copper-molybdenum elsewhere in the world. Finally, the comparison of geochemical anomalies copper with rock units and alteration zones showed that atmospheric waters had washed out the copper in some of these zones and probably the supergene zone was formed in depth as porphyry copper-molybdenum deposit.

The book "Mineralogy and Petrology" is an attempt to association of knowledge of Crystallography and Mineralogy with those of Petrology, in a treating "sui generis" crystal-mineral-rock. The book it is meant to students and specialists in the fields of oil and gas engineering, geology, environmental engineering and material science. It was conceived as a semester course and covers all aspects of the three most important branches of Mineralogy: Crystallography, Crystallogenesis, Crystallochemistry, and Petrology respectively: Genesis of minerals and rocks in igneous, metamorphic and sedimentary processes. The book is divided into several chapters: Crystallography, Crystallogenesis, Crystallochemistry, Petrology, enjoying of a rich latest references. They are preceded by a brief introduction to Mineralogy, setting out the general terms relating to the use of minerals, evolution of knowledge about minerals and history of the development of Mineralogy as science in Romania. Without neglecting the main minerals that are part of other mineral classes (native elements, sulfides, oxides and hydroxides, halides, carbonates, sulfates, phosphates), the authors insists on the crystallochemistry of silicate minerals with the largest share in the earth's crust and, generally less known than other classes of minerals. Chapter "Petrology" is treated in an original manner, the processes of formation of the rocks are presented simultaneously with the processes of forming of minerals thus projecting the links between mineral genesis, rock genesis (mineral associations) and further accumulation genesis of useful minerals. Briefly are presented the concepts of magmatic petrology, metamorphic and sedimentary processes involved in the forming of different types of rocks and highlighted by diagrams, figures, diagrams, tables. The concepts related to rocks or processes (names, descriptions, classifications) were adapted to the recommendations of the Subcommittees of systematics of the igneous and metamorphic rocks (SSIR and SCMR) from IUGS. The book reveals a varied information, briefly presented, logically, is rich illustrated with figures, charts and tables, being useful both students in the field of mineralogy and petrology, and specialists in production and research.

Seu conteúdo foi revisado pelo Comitê Técnico do IV SimBGf, mas não necessariamente representa a opinião da SBGf ou de seus associados. É proibida a reprodução total ou parcial deste material para propósitos comerciais sem prévia autorização da SBGf.

We report new major element, trace element, isotope ratio, and geochronological data on the Galfipagos Archipelago. Magmas erupted from the large western volcanos are generally moderately fractionated tholeiites of uniform composition; those erupted on other islands are compositionally diverse, ranging from tholeiites to picritic basanitoids. While these volcanos do not form a strictly linear age progressive chain, the ages of the oldest dated flows on any given volcano do form a reasonable progression from youngest in the west to oldest in the east, consistent with motion of the Nazca plate with respect to the fixed hotspot reference frame. lsotope ratios in the Galfipagos display a considerable range, from values typical of mid-ocean ridge basalt on Genovesa (87Sr/86Sr: 0.70259, end: +9.4, 206pb/204pb: ! 8.44), to typical oceanic island values on Floreana (87Sr/86Sr: 0.70366, oeNd: +5.2, 206pb/204pb: 20.0). La/Sm N ranges from 0.45 to 6.7; other incompatible element abundances and ratios show comparable ranges. Isotope and incompatible element ratios define a horseshoe pattern with the most depleted signatures in the center of the Galfipagos Archipelago and the more enriched signatures on the eastern, northern, and southern periphery. These isotope and incompatible element patterns appear to reflect thermal entrainment of asthenosphere by the Galfipagos plume as it experiences velocity shear in the uppermost asthenosphere. Both north-south heterogeneity within the plume itself and regional variations in degree and depth of melting also affect magma compositions. Rare earth systematics indicate that melting beneath the Galfipagos begins in the garnet peridotite stability field, except beneath the southern islands, where melting may occur entirely in the spinel peridotite stability field. The greatest degree of melting occurs beneath the central western volcanos and decreases both to the east and to the north and south. Sis. 0, FeB. 0, and NaB. 0 values are generally consistent with these inferences. This suggests that interaction between the plume and surrounding asthenosphere results in significant cooling of the plume. Superimposed on this thermal pattern produced by plume-asthenosphere interaction is a tendency for melting to be less extensive and to occur at shallower depths to the south, presumably reflecting a decrease in ambient asthenospheric temperatures away from the Galfipagos Spreading Center.

The siliceous sinter deposits of El Tatio geothermal field in northern Chile have been examined petrographically and
mineralogically. These sinters consist of amorphous silica (opal-A) deposited around hot springs and geysers from nearly
neutral, silica-saturated, sodium chloride waters. Water cooling and evaporation to dryness are the main processes that control
the opal-A deposition in both subaqueous and subaerial settings, in close spatial relation to microbial communities. All
fingerprints of organisms observed in the studied sinter samples represent microbes and suggest that the microbial community is
moderately diverse (cyanobacteria, green bacteria, and diatoms). The most important ecological parameter is the temperature
gradient, which is closely related to the observed depositional settings: 1) Geyser setting: water temperature=70–86 8C (boiling
point at El Tatio: 4200 m a.s.l.); coarse laminated sinter macrostructure with rapid local variations; biota comprises nonphotosynthetic
hyperthermophilic bacteria. 2) Splash areas around geysers: water temperature=60–75 8C; laminated spicule
and column macrostructure, locally forming cupolas (b30 cm); predominant Synechococcus-like cyanobacteria. 3) Hot spring
setting: water temperature=40–60 8C; laminated spicules and columns and subspherical oncoids characterize the sinter
macrostructure; filamentous cyanobacteria Phormidium and diatoms (e.g., Synedra sp.) are the most characteristic microbes.
4) Discharge environments: water temperature=20–40 8C; sinter composed of laminated spicules and oncoids of varied shape;
cyanobacterial mats of Phormidium and Calothrix and diatoms (e.g., Synedra sp.) are abundant. El Tatio is a natural laboratory
of great interest because the sedimentary macrostructures and microtextures reflect the geological and biological processes
involved in the primary deposition and early diagenesis of siliceous sinters.

Decades of field and microscope studies and more recent quantitative geochemical analyses have resulted in a vast, and sometimes overwhelming, array of nomenclature and terminology associated with igneous rocks. Under the auspices of the International Union of Geological Sciences (IUGS), a group of petrologists from around the world has laboured for more than 30 years to collate these terms, gain international agreement on their usage, and reassess the methods by which we categorize and name igneous rocks.

Las rocas ígneas son aquellas formadas a partir de un producto fundido procedente del interior de la tierra. En petrología se emplean dos términos para hacer alusión a una roca fundida: Magma, el cual corresponde a un término general que engloba una mezcla de fundido y cristales que pueden estar suspendidos en su interior y Fundido, el cual se refiere exclusivamente al material líquido, excluyendo cualquier material sólido. Conforme un cuerpo de magma asciende y se aproxima a la superficie, comúnmente contendrá burbujas de gas (formadas por gas que ha escapado del fundido debido a la caída en la presión producida durante el ascenso) y fenocristales. Debido a esto, el término " magma " es utilizado para englobar fundido, cristales y cualquier burbuja de gas presente. Cuando este material es expulsado en la superficie, pierde parte de este gas, liberándolo hacia la atmósfera. El material restante es comúnmente denominado " lava ". Los magmas son originalmente formados por fusión al interior de la tierra. La fusión inicial comúnmente toma lugar en el manto, y al atravesar la corteza continental podría eventualmente causar fusión adicional de ésta, incorporando parte de sus elementos al complejo sistema magmático. En regiones oceánicas y continentales, los magmas se enfrían y experimentan cristalización parcial dentro de la corteza en reservorios denominados " cámaras magmáticas " , dando así lugar a la amplia variedad de composiciones de magma que eventualmente pudieran ser extruidos en la superficie. La descripción de una roca ígnea se realiza en base a su fábrica, es decir todas aquellas propiedades no composicionales de la roca, lo cual comprende texturas y estructuras de gran escala. Las texturas (también llamadas microestructuras) están basadas en la proporción de vidrio relativo a los granos minerales y sus tamaños, formas y arreglos mutuos que son observados a escala de una muestra de mano o una lámina delgada observada bajo el microscopio. Las texturas que pueden observarse en una roca ígnea, resultan de un número de procesos que pueden ser agrupados en dos principales categorías:  Texturas primarias: surgen durante la cristalización y son desarrolladas debido a la interacción ocurrida entre los minerales y el fundido magmático.

Pressure is one of the most important parameters to be quantified in geological problems. However, in metamorphic systems the pressure is usually calculated with two different approaches. One pressure calculation is based on petrological phase equilibria and this pressure is often termed thermodynamic pressure. The other calculation is based on continuum mechanics, which provides a mean stress that is commonly used to estimate the thermodynamic pressure. Both thermodynamic pressure calculations can be justified by the accuracy and applicability of the results. Here, we consider systems with low differential stress (<1 kbar) and no irreversible volumetric deformation, and refer to them as conventional systems. We investigate the relationship between mean stress and thermodynamic pressure. We discuss the meaning of thermodynamic pressure and its calculation for irreversible processes such as viscous deformation and heat conduction, which exhibit entropy production. Moreover, it is demonstrated that the mean stress for incompressible viscous deformation is essentially equal to the mean stress for the corresponding viscous deformation with elastic compressibility, if the characteristic time of deformation is five times longer than the Maxwell viscoelastic relaxation time that is equal to the ratio of shear viscosity to bulk modulus. For typical lithospheric rocks, this Maxwell time is smaller than c. 10,000 years. Therefore, numerical simulations of long‐term (>10 kyr) geodynamic processes, employing incompressible deformation, provide mean stress values that are close to the mean‐stress value associated with elastic compressibility. Finally, we show that for conventional systems the mean stress is essentially equal to the thermodynamic pressure. However, mean stress and, hence, thermodynamic pressure can be significantly different from the lithostatic pressure.

This work proposes a 2.5D modeling for a section crossing a segment of the Transbrasiliano Lineament in the southern part of Parnaiba Basin, NE Brazil-based on joint inversion of magnetic and gravimetric data. This study points out that the thickness of the sedimentary cover is related to tectonic features such as graben and horsts. Euler deconvolution technique was used in this work aiming to reduce ambiguities of the model as well as to contribute for a better quantification of anomalous source depths. A previous qualitative analysis was necessary to obtain an understanding of different types of sources that might be responsible for magnetic and gravimetric signatures in the area. This analysis was important to a better interpretation of the anomalous sources as long as not all given solutions offered by the Euler technique are those that are aimed to be analyzed.

Batuan sedimen atau sedimentary rocks adalah batuan yang terbentuk dari campuran material batuan yang telah ada sebelumnya kemudian mengalami proses sedimentasi yang meliputi pelapukan, pengangkutan dan pengendapan. Batuan sedimen atau yang dikenal juga dengan batuan endapan merupakan batuan yang terbentuk dari material erosi yang mengalami proses pengendapan, materi erosi tersebut sebelumnya mengalami proses pengangkutan dengan cara terdorong, terbawa dalam bentuk suspensi ataupun melarut. Keterdapatan batuan sedimen lebih sedikit di kerak bumi jika dibandingkan dengan batuan beku, yaitu sekitar 5%, namun 75% batuan sedimen meliputi permukaan bumi.
Batuan sedimen memiliki sifat tertentu yaitu menunjukan adanya bidang perlapisan yang membuktikan telah terjadinya proses sedimentasi, pada suatu batuan butir-butir telah lepas dari batuan karena memiliki sifat klastik, sifat jejak yang menunjukan adanya bekas tanda kehidupan, dan jika batuan sedimen hanya tersusun oleh satu mineral maka akan berbentuk hablur. Sifat-sifat batuan sedimen ini pada intinya diakibatkan oleh proses sedimentasi yang meliputi pelapukan, pengangkutan dan pengendapan.

Metamorfismo: Proceso que implica cambios en la mineralogía y/o microestructura de una roca en estado sólido. El cambio es esencialmente debido a una adaptación de la roca a condiciones físicas que difieren de aquellas bajo las que la roca parental se formó y que difieren de las condiciones físicas que normalmente existen en la superficie de la tierra y en la zona de diagénesis.

Batuan beku dapat diklasifikasikan berdasarkan mineral penyusunnya. Sebagaimana diketahui, mineral penyusun batuan beku terdiri atas 3 jenis mineral, mineral utama (primer), mineral sekunder dan mineral asosiasi (tambahan). Mineral utama merupakan mineral yang keterdapatannya mendominasi pada batuan beku tersebut, misalnya kuarsa, olivine, plagioklas, ortoklas, piroksin, ampibol, mineral utama biasanya menentukan penamaan pada batuan beku. Mineral sekunder merupakan mineral yang terbentuk yang berasal dari mineral utama yang diakibatkan oleh pelapukan atau dari sisa-sisa magma, contohnya klorit, kalsit dan kaolin. Mineral asesori atau mineral tambahan merupakan mineral yang keterdapatannya hanya sedikit, bersifat ikutan pada mineral utama dan tidak mempengaruhi penamaan batuan beku, misalnya magnetit, hematit dan rutil.

Irreducible water saturation value is an indication of total volume of oil and water producible from a reservoir. It also influences the production rate from that reservoir. Irreducible water saturation (sometimes called critical water saturation) defines the maximum water saturation that a formation with a given permeability and porosity can retain without producing water. This water, although present, is held in place by capillary forces and will not flow. Critical water saturations are usually determined through special core analysis. The critical water value should be compared to the reservoir's in-place water saturation calculated from downhole electric logs. If the in-place water saturation does not exceed the critical value, then the well will produce only hydrocarbons. These saturation comparisons are particularly important in low permeability reservoirs, where critical water saturation can exceed 60% while still producing only hydrocarbons.

Modul Praktikum Petrologi 2015 Laboratorium Petrologi Universitas Pembangunan Nasional "Veteran" Yogyakarta 2015 1 BAB I BATUAN BEKU Batuan beku adalah batuan yang terjadi dari pembekuan larutan silikat cair liat , pijar, bersifat mudah bergerak yang kita kenal dengan nama magma. Penggolongan batuan beku dapat dikelompokkan menjadi 3 (tiga) yaitu 1. Berdasarkan genetik batuan, 2. Berdasarkan senyawa kimia yang terkandung dan 3. Berdasarkan susunan mineraloginya. Batuan beku dapat dibagi menjadi: A. Batuan Beku Ekstrusi Batuan beku sebagai hasil pembekuan magma yang keluar di atas permukaan bumi baik di darat maupun di bawah muka air laut. Pada saat mengalir di permukaan masa tersebut membeku relatif cepat dengan melepaskan kandungan gasnya. Oleh karena itu sering memperlihatkan struktur aliran dan banyak lubang gasnya (vesikuler). Magma yang keluar di permukaan atau lava setidaknya ada 2 jenis: Lava Aa dan Lava Pahoehoe. Lava Aa terbentuk dari masa yang kental sedangkan lava Pahoehoe terbentuk oleh masa yang encer B. Batuan Beku Intrusi Batuan hasil pembekuan magma di bawah permukaan bumi. Ukuran mineralnya kasar, > 1 mm atau 5 mm. Ga mb ar 1 .1 Jenis -Jen is In stru si Modul Praktikum Petrologi 2015 Laboratorium Petrologi Universitas Pembangunan Nasional "Veteran" Yogyakarta 2015 2 1. Berbentuk tidak teratur dengan dinding yang curam dan tidak diketahui batas bawahnya. Yang memiliki penyebaran > 100 km 2 disebut batolith, yang kurang dari 100 km 2 dikenal dengan stock sedangkan yang lebih kecil dan relatif membulat disebut boss. Ketiganya merupakan peristilahan dalam batuan plutonik. 2. Intrusi berbentuk tabular yang memotong struktur setempat (diskordan) disebut dyke/korok sedangkan yang konkordan disebut sill atan lakolit kalau cembung ke atas. 3. Intrusi berdimensi kecil dan membulat sering dikenal dengan intrusi silinder atau pipa.

A detailed geological mapping of Kurafe Hausawa and environs, part of Keffi sheet
208 NW was carried out on a scale of 1: 12,500. It is part of the Nigerian Basement
Complex, situated within latitude 8°50'40"N and 8°47'50"N and longitudes 7°39'13"E
and 7°37'48"E and covers an extent of 12.5 km2
. The aim of this research work is to
identify the rock types and generate a detailed geological map of Kurafe Hausawa and
its environs. The research methodology includes; field mapping, laboratory study and
petrographic analysis. The mapped area is dominated by the gneisses (granitic gneiss,
banded gneiss and porphyroblastic gneiss), and the schists along with andesite
respectively. Petrographic analysis of the rocks in the study area further uncovers
mineral assemblages such as biotite, muscovite, quartz, plagioclase as the most
common minerals, with little of opaque and accessory minerals such as zircon and
garnet. Structural features noticed include faults, joints, veins, foliations and folds,
which generally trend in NE-SW, NW-SE directions. The hydrogeology of the
mapped area is mainly the surface water resources, with a network of stream channels
all linked with the major River Uke. Economically, the study area comprises of rocks
and mineral aggregates.

Pada suatu mineral, biasanya tersusun oleh kristal yang sama susunan kimianya namun berbeda dalam struktur kristalnya, kemampuan mineral ini dinamakan polimorfisme. Polimorfisme terjadi akibat struktur kristal dipengaruhi oleh suhu dan tekanan pada lingkungan pertumbuhannya. Mineral mungkin memiliki kristal yang sama namun pada suatu kasus tertentu susunan kimianya berbeda, contohnya kianit-silimanit-andalusit, kalsit-aragonit, dan intan-grafit.