Ultrabasic Igneous Rocks Research Articles

Mineralogy and Geochemistry Characteristics of Tanjero Formation in Selected Locations, Northeast of Iraq

Tanjero Formation (belongs to the upper cretaceous sequences( which are exposed in the northeast part of Iraq within the high folded zone. In this study, the mineralogy and geochemistry of the formation are examined by XRD and XRF techniques. The mineralogical study reveals that Calcite is the main mineral making the carbonate rocks of the formation with subordinate minerals of quartz and a low quantity of clay minerals (Chlorite, montmorillonite, and illite). Geochemical results revealed high levels of silica and calcium, aluminum, magnesium, and iron oxides. High concentrations of some trace elements (Cr, V) reflect their origin of basic and ultrabasic igneous rocks. The high content of Mn in the carbonate rocks of the formation reflects the depositional environment which is a deep marine environment. Most trace elements in the present study have positive correlations with SiO2, Al2O3, and K2O suggesting their association with clay minerals.

GEOMORPHOLOGY AND CHARACTERISTICS OF NICKEL LATERITE IN BAINGKETE VILLAGE, MAKBON DISTRICT, SORONG REGENCY WEST PAPUA PROVINCE

Nickel deposits geologically came from weathering of abducted ultrabasic igneous rock. The rock is exposed during removal, followed by a geomorphological process that develops laterazation. Geologically the Makbon area is on the path of the Sorong horizontal fault field which has been active since the beginning of the Miocene. The dominant Sorong fault movement to the west exposed ocean floor rocks including blocks of ultrabasic rock. To determine the mineralization of nickel laterite in the Makbon area, this study combines mapping and surface geological observation methods with XRF analysis in the laboratory. The results of the study are known that the research area is composed of six land formations, namely the Makbon Fault Block Ridge, Baingkete Fault Block Ridge, Bancuh Baingkete Hills, Baingkete Bald Mountain Bancuh Hills, Makbon Fault Structure Denudation Plain, and Dore Bay Hills. Geomorphological control of the distribution of laterite nickel on steep slopes produces a thin, thickened laterite layer on the topography of the ramps. The characteristics of laterite nickel deposits in Baingkete Village are Type A deposits (Mg-Ni Silicate), on serpentinite bedrock, which consist of laterite profiles of limonite zone, saprolite zone, and bedrock zone

Preparation of continuous silicate fiber from pyroxene and K-feldspar mixture

Mixtures of pyroxene and K-feldspar instead of basalt rock were adopted to study the formation of continuous basalt fiber. Changing in mass ratio of the two minerals simulated acidic to ultrabasic igneous rocks. Within a specific composition range, continuous fiber was successfully prepared, whose fibration property was governed by both the viscosity and depolymerization degree (NBO/T) of the silicate melts. FT-IR and Raman spectra provided detailed structural information on the correlations between fibration property and the connection of silicate framework units. A proper ratio and arrangement of Q2 ([Si2O6]4−) and Q3 ([Si2O7]6−) was considered a key factor influencing the formation and tensile strength of the fiber. The results in present work also sheds light on a new route to prepare analogous basalt fiber by a proper combination of different industrial or mining silicates instead of exploiting new basalt rocks.

Geochemical characterization of the Sutlegen bauxite deposit, SW Antalya

Purpose.The purpose is to determine geological and geochemical characteristics of the Sutlegen (Antalya, Turkey) bauxites, to identify the elements that played a major role in their formation. Methods. X-ray diffraction (XRD) mineral phase analysis, X-ray fluorescence (XRF) elemental analysis, plasma-mass spectrometry (ICP-MS), the petrographic and mineralogical analyses, and multivariate statistical methods were used. Findings. The major element content of the ore was determined as Al2O3 (60-35.2 wt%), SiO2 (39.5-0.2 wt%), Fe2O3 (48.4-19.5 wt%), TiO2 (36.9-16 wt%), and P2O5 (0.5-0.1 wt%). The Sutlegen region, which shows epirogenetic action with the uplift of the earth's crust, is generally rich in neritic carbonates. It was revealed that the bauxite ores have undergone moderate and strong laterization as a result of the deferruginization in the environment, and they were classified into four groups as lateritic, ferritic, kaolinitic, and bauxite. The increase in the aluminosilicate minerals, which were formed during the formation of bauxite in the environment was found to be directly proportional to the laterization processes. In this context, it was considered that the lateritic material that was firstly formed in the environment filled the cavities and pores of the karst-type limestones and sedimentary units in the region by superficial transfer phenomena. The bivariate diagrams of Log Cr vs. Log Ni revealed that the bauxite that formed in the region had an ultrabasic source. Originality. In literature, no scientific studies have been found on bauxite mineralization in the Sutlegen deposits that have been operated for a long period. Practical implications. In this context, the geochemical characteristics of bauxites revealed that the source of the laterization process in the region was the ultrabasic igneous rocks. The lateritic material moved by superficial transfer was accumulated on sandstone, claystone, siltstone, and limestone and in karstic cavities; then, it formed karstic bauxite (kaolinitic and bauxite) of different classifications due to the effect of metamorphism.

Enrichment of Platinum Group Elements in Lower Cambrian Polymetallic Black Shale, SE Yangtze Block, China

Platinum group elements (PGEs) occur mainly in basic–ultrabasic igneous rocks and are concentrated by the differentiation and crystallization of magma. Thin polymetallic layers including Ni, Mo, V, PGEs, and rare-earth elements are widely developed in lower Cambrian black shales in southern China. The PGE contents in such layers may not be economically significant but are still unusually enriched. PGE enrichment mechanisms have not been widely studied, but here the PGE compositions of polymetallic layers in the Shuidong (Nayong) and Niuchang (Weng’an) sections of the SE Yangtze block in China were determined, and results compared with published data for the region. Results indicate that PGEs are enriched in the polymetallic layers, whereas the surrounding country rocks are barren. The ΣPGE contents in the Shuidong Ni–Mo deposits are generally lower than in the Niuchang V deposits. PGE distribution patterns in the polymetallic layers are similar to those in basic–ultrabasic rocks, indicating that such rocks played a role in the PGE enrichment. Oceanic hypoxia during the Sinian–Cambrian transition resulted in the production of large amounts of organic matter and H2S in the ocean. When high-salinity brine reached the ocean bottom, rapid changes in Eh–pH conditions caused enrichment of metals at the sediment–seawater interface, and this enrichment was later enhanced during diagenesis.

Provenance discrimination of upper Yangtze River basin sediments: New insights from heavy mineral signatures and detrital magnetite geochemistry

Magnetite is typomorphic, and its crystal textures and chemical fingerprint form unique signatures that can be used to determine sediment provenance. Determination of the provenance of sediments in the upper Yangtze River is critical for understanding its evolution and the uplift of the Tibetan Plateau. In this study, petrographic analysis and electron-probe microanalysis (EPMA) of 800 detrital magnetite grains were performed to differentiate the provenance of sediments within the mainstream and major tributaries of the upper Yangtze River catchment. Chemical analyses show that the elemental composition of magnetite grains shows pronounced variations among the different sections of the mainstream and tributaries. Based on the observed chemical fingerprints, we infer that the source rocks control the elemental composition of magnetite grains. The magnetite contribution is closely related to the tectonics, climate, and erosion of parent rocks within different drainage basins. Magnetite from the trunk stream of the Jinsha River is found to be a significant contributor to the upper Yangtze River. Magnetite grains of the upper Jinsha River are primarily derived from source areas composed of silicic plutonic rocks and ophiolite lithologies that crop out on the SE Tibetan Plateau. Magnetite grains within the sands of the lower Jinshajiang sediments are characterized by high concentrations of Ti, Mg, Cr, Al, and Mn, and are derived from the widely distributed Emeishan flood basalts and Pan-Xi layered basic–ultrabasic igneous rocks. This source is also a major contributor of magnetite to the upper Yangtze River, and the parent rock distributed in this region is of typomorphic significance to the development of the Yangtze River. The origin of magnetite grains in the tributaries depends on the parent rocks distributed in their catchments. In summary, the presence of detrital magnetite grains provides valuable information for discriminating the provenance of sediments in the upper Yangtze River drainage basins.

Fuzzy petrology in the origin of carbonatitic/pseudocarbonatitic Ca-rich ultrabasic magma at Polino (central Italy)

The small upper Pleistocene diatreme of Polino (central Italy) is known in literature as one of the few monticellite alvikites (volcanic Ca-carbonatite) worldwide. This outcrop belongs to the Umbria-Latium Ultra-alkaline District (ULUD), an area characterized by scattered and small-volume strongly SiO2-undersaturated ultrabasic igneous rocks located in the axial sector of the Apennine Mts. in central Italy. Petrographic and mineralogical evidences indicate that Polino olivine and phlogopite are liquidus phases rather than mantle xenocrysts as instead reported in literature. The presence of monticellite as rim of olivine phenocrysts and as groundmass phase indicates its late appearance in magma chambers at shallow depths, as demonstrated by experimental studies too. The absence of plagioclase and clinopyroxene along with the extremely MgO-rich composition of olivine (Fo92–94) and phlogopite (average Mg# ~93) suggest for Polino magmas an origin from a carbonated H2O-bearing mantle source at depths at least of 90–100 km, in the magnesite stability field. In contrast with what reported in literature, the ultimate strongly ultrabasic Ca-rich whole-rock composition (~15–25 wt% SiO2, ~31–40 wt% CaO) and the abundant modal groundmass calcite are not pristine features of Polino magma. We propose that the observed mineral assemblage and whole-rock compositions result mostly from the assimilation of limestones by an ultrabasic melt at a depth of ~5 km. A reaction involving liquidus olivine + limestone producing monticellite + CO2 vapour + calcite is at the base of the origin of the Polino pseudocarbonatitic igneous rocks.

Sedimentology and detrital zircon geochronology of the Nanduan Formation (Carboniferous) of the Changning-Menglian Belt: indications for the evolution of Paleo-Tethys in western Yunnan, China

The Changning-Menglian Belt in western Yunnan, China, has been considered for decades as a remnant of Paleo-Tethys in this region. However, the understanding of the geological evolution of the belt remains sketchy and incomplete. As a significant component of the stratigraphic successions in the eastern part of the belt, the siliciclastic Nanduan Formation preserved essential information of the developing history of the belt. Petrologic studies of the formation show that it was deposited in a neritic environment. The increase of mudstone beds and decrease of grain size of sandstones upwards suggest a gradual deepening of sedimentary environment. Petrographic and geochemical characteristics of sandstones show that they were derived from mature continental provenance and deposited in a passive continental margin setting. Detrital zircon ages of the formation range from 362 to 3685 Ma. The youngest detrital zircon age (362.2 ± 5.5 Ma) confines the deposition age of the sandstones to being younger than the latest Devonian. Dominant age populations of ca. 950 Ma and ca. 550 Ma can be correlated with the magmatic events that occurred in Eastern Ghats-northern Prince Charles (India–Antarctica) (ca. 950 Ma) and Pan-African orogens (Australia–India) (ca. 550 Ma), which are considered, therefore, to be the main provenance of the Nanduan Formation. These results let us consider that the Nanduan Formation and the underlying Lancang Group were formed on the margin of the Baoshan-Shan Block (therefore, autochthonous), and the Carboniferous‒Permian limestones of seamount resemblance, the oceanic bedded cherts, and basic and ultra-basic igneous rocks in the central zone of the belt are overthrusted slices (allochthonous).

Manganilmenite in the Magnetite Ore Body from Pokphur Area of Nagaland, North East India and the Possibility of Microdiamonds in the Ophiolites of Indo-Myanmar Ranges

Manganilmenite is found to be associated with the magnetite ore body of Pokphur area in the Nagaland ophiolites, North East India. There is perhaps no earlier description of the mineral from the Indian subcontinent. It occurs as an accessory mineral with magnetite and Fe-chlorite (chamosite). Electron probe micro-analytical data reveal that the mineral contains 5.6-8.5 wt% MnO and traces of MgO, ZnO and Cr2O3, while the TiO2 content remains within narrow limits of 50-53 wt%. The calculated pyrophanite end-member varies from 13% to 18%. Although the magnetite body of Pokphur has been reasonably proved to be a hydrothermally altered product of basic and ultrabasic igneous rocks, and most of the minerals in the magnetite body are supergene in nature, different end-member compositions of mangan ilmenite indicate that it has originally crystallized with the basic suite of rocks and has survived the alteration process with only marginal effects. Since manganilmenite has been considered as a diamond indicator mineral and ophiolites are a newly documented host of microdiamonds elsewhere in the world, the presence of manganilmenite in the Pokphur magnetite hints towards occurrence of microdiamonds in the ophiolite suite of rocks of the Indo-Myanmar ranges.

Provenance of heavy minerals from recent sediments of Balakyan River, Kurdistan Region, Iraq

Heavy mineral assemblages of the sediments in Balakyan River have been studied to determine their concentrations and provenance. Twelve sediment samples were analyzed for heavy mineral assemblage determination. The unstable heavy minerals (pyroxene and amphibole) represent more than 50%. The mineral chemistry and petrographic studies refer to the predominant clinopyroxene mineral is diopside. Actinolite, tremolite, and magnesiohornblende are common calc-amphibole in the sediments. The ultrastable heavy minerals are present in trace amounts. According to the mineral chemistry the clinopyroxene is derived from basic igneous rocks crystallized at 1150-1220⁰C and low pressure. Amphibole and epidote crystallized under low temperature and/or formed under low grade metamorphism. The detrital chromian spinel is derived from basic and ultrabasic igneous rocks of Alpine type peridotite formed in fore-arc. The probable source of these assemblages is Ophiolite Complex to the north of the studied area (north Iraq) and igneous parts of Walash Series and Red Bed Series also the sedimentary rocks of Shiranish and Tanjero formations.

Petrogenesis of dunites of the Guli ultrabasic massif (northern Siberian Platform)

New data on silicate melt inclusions in accessory Cr-spinel have given an insight into the physicochemical conditions of petrogenesis of dunites of the Guli massif (northern Siberian Platform). Studies of the inclusions demonstrate the contribution of high-Mg (16-22 wt.% MgO) alkali-picritic and picrobasaltic melts to the crystallization of these ultrabasic rocks. During the intrachamber crystallization of the Guli massif dunites, the composition of magmatic systems evolved from picrite-meimechite (with olivine forming at 1500-1380 °C and Cr-spinel forming at 1420-1360 °C) to picrobasalt. Comparison with well-known associations of ultrabasic igneous rocks has shown that melt inclusions in Cr-spinel from the Guli massif dunites are similar to inclusions in olivine phenocrysts from meimechites in the contents of most petrochemical components and in the distribution of indicator trace and rare-earth elements. In general, the new information on melt inclusions testifies that the Guli massif dunites formed with the participation of high-temperature high-Mg melts similar in composition to meimechite magmas.

Plate tectonic settings for Precambrian basic rocks from Brazil by multidimensional tectonomagmatic discrimination diagrams and their limitations

Multidimensional discrimination diagrams (2006–2011) for basic and ultrabasic igneous rocks were applied to Precambrian rock suites from the Amazonian and São Francisco cratons, and the Tocantins Province, Brazil, to infer their possible tectonic settings. The chosen study cases in the Amazonian craton include the ca. 3.0 Ga metabasalts of the Identidade greenstone belt, 1.87–1.80 Ga Parauapebas anorogenic basalt-rhyolite dikes, 1.86–1.82 Ga Rio Branco anorogenic gabbro-basalt association, ca. 1.76–1.74 Ga Aripuanã and Teles Pires intracratonic basalt-felsic volcanic associations, and 1.76–1.74 Ga Jamari and 1.60–1.53 Ga Serra da Providência arc-related gabbroic rocks. In the São Francisco craton, we selected 1.48 Ga arc-related amphibolites of the Rio Capim greenstone belt, continental mafic dikes of Uauá (2.6 Ga), Curaçá and Chapada Diamantina (1.5 Ga), and Espinhaço (ca. 1.0 Ga). In the Tocantins Province, ca. 3.0 Ga komatiites associated with oceanic basalts of the Crixás and Guarinos greenstone belts were studied. The application of the diagrams generally provided consistent results with the authors’ proposed tectonic settings based on field relationships and geochemical data. The exceptions are some within-plate (continental) mafic dikes and basalts for which our diagrams do not work well. For comparison, we also used two ternary and two bivariate traditional discrimination diagrams for the data from the Amazonian craton, whose results were poorer than the newer multidimensional diagrams.

Early Permian Tarim Large Igneous Province in northwest China

Tarim Large Igneous Province (TLIP) is the second Late Paleozoic LIPs in China after the recognition of Emeishan LIP, and is a hot research topic in geosciences. On the basis of the analysis of research history about TLIP, this paper summarizes the research result during last twenty years and suggests the key research area in the future. The residual distribution range of TLIP is up to 250000 km2, and the largest residual thickness is 780 m. The eruption of basalt happened during 290–288 Ma and belongs to LIPs magmatic event with fast eruption of magma. The lithological units of the TLIP include basalt, diabase, layered intrusive rock, breccia pipe mica-olivine pyroxenite, olivine pyroxenite, gabbro, ultramafic dyke, quartz syenite, quartz syenite porphyry and bimodal dyke. The basalt and diabase of TLIP exhibit OIB-like trace element patterns and enrichment of LILE and HFSE, and mainly belong to high TiO2 series. There is an obvious difference in isotope among the basalt from Keping and the basalt and dibase from the northern Tarim Basin. The basalt from Keping with negative ɛ Nd and high REE value derives from enriched mantle, and the diabase and basalt from the northern Tarim Basin with positive ɛ Nd and low REE value are related to depleted mantle. The crust uplifting in the Early Permian and the development of picrite and large scale dyke and formation of large scale V-Ti-Magnetite deposit in Wajilitag area support the view that the TLIP is related to mantle plume. The TLIP has a temporal-spatial relationship with Permian basic to ultra-basic igneous rock, which is distributed widely in Central Asia, and they represent a tectono-magmatic event with very important geodynamic setting. This paper also suggests that the deep geological process, the relation with mantle plume, mineralization, the relation with environmental change and biological evolution, and the geodynamics of the TLIP will be the key research topics in the future.

Interactive influences of climate and parent material on soil microbial community structure in Bornean tropical forest ecosystems

AbstractClimate and parent material strongly control vegetation structure and function, yet their control over the belowground microbial community is poorly understood. We assessed variation in microbial lipid profiles in undisturbed forest soils (organic and surface mineral horizons) along an altitudinal gradient (700, 1,700, and 2,700 m a.s.l. mean annual temperature of 12–24°C) on two contrasting parent materials (acidic metasedimentary vs. ultrabasic igneous rock) in Mt. Kinabalu, Borneo. Soil organic carbon and nitrogen concentrations were generally higher at higher altitudes and, within a site, at upper soil horizons. Soil pH ranged from 3.9 to 5.3, with higher values for the ultrabasic soils especially at higher altitudes. The major shifts in microbial community structure observed were the decline in the ratio of fungal to bacterial lipid markers both with increasing soil depth and decreasing altitude. The positive correlation between this ratio with soil C and N concentrations suggested a strong substrate control in accord with the literature from mid to high‐latitude ecosystems. Principal component analysis using seven groups of signature lipids suggested a significant altitude by parent material interaction—the significant difference in microbial community structure between the two rock types found at 2,700‐m sites developed on weakly weathered soils diminished with decreasing altitude towards 700‐m sites where soils were strongly weathered. These results are consistent with the hypothesis that parent material effect on soil microbial community (either directly via soil geochemistry or indirectly via floristic composition) is stronger at an earlier stage of ecosystem development.

Climate and parent material controls on organic matter storage in surface soils: A three-pool, density-separation approach

Physically- and biochemically-distinct fractions of soil organic matter (SOM) can be separated by density to yield: (i) low-density plant detritus fraction easily separable from soil minerals (f-LF), (ii) low-density materials strongly associated with minerals (m-LF), and (iii) high-density fraction (HF) rich in microbially-processed organic matter strongly associated with minerals. The factors controlling the pool size and chemistry in these fractions, especially those in m-LF, are unclear. We examined the influence of climate and parent material on SOM in these fractions using two sets of forest soils (0–10 cm mineral horizon) developed from contrasting parent materials (metasedimentary vs. ultrabasic igneous rock) along an altitudinal gradient in Mt. Kinabalu, Borneo. From 700 m to upper altitudes (1700, 2700 m), where mean annual temperature decreases from 24 to 12 °C with roughly constant rainfall, surface soil C stocks on both parent materials increased from 2.6–2.8 to 5.4–7.5 kg m − 2 with progressively greater proportions in m-LF and, to less extent, fresher plant detritus fractions. In HF, C and N concentrations increased with altitude though their stocks were roughly constant due to progressively lower bulk density. Labile C assessed by laboratory incubation of bulk soils correlated better with C concentrations in the two LF pools than in HF, especially at the lowest altitude where most SOM is strongly associated with minerals as HF. These results suggest that LF pools are more labile and more sensitive to altitude-induced, climate differences as compared to the HF pool that is protected by the mineral matrix. The C:N ratios of HF on metasedimentary rock increased with altitude (11 to 17) while those on ultrabasic rock remained essentially constant (14–15), implying interactive influence of altitude and parent material on stoichiometry. Unusually high C:N and alkyl-C in m-LF were found in mid-altitude soils, suggesting selective preservation of inherently recalcitrant materials in addition to, or instead of, mineral coating or aggregate occlusion of partially-degraded LF by microbial metabolites.

Dominance of lithogenic effect for nickel, cobalt, chromium and mercury as found in freshly deposited sediments of the river Subernarekha, India

The importance of study of heavy metal distribution in river sediments is a component in understanding the exogenic cycling as well as in assessing the effect of anthropogenic influences of the elements. In India, the river Subernarekha flows over Precambrian terrain of Singhbhum craton in the eastern India. The geological succession in this part of India is through (1) iron ore series, (2) ultrabasic igneous rocks, (3) diorite, (4) granite, (5) newer dolerites, (6) newer tertiary and (7) alluvium. The first four groups belong to the Archaean era, and the representative is the iron ore series consisting of iron ore, manganese and chromite which are abundantly present. The primary rock types are schist and quartzite layers. One main tributary, the Kharkhai flow through granite and schist and quartzite layers. Two important creeks are Gurma and Garra, respectively. The former after originating in basic igneous area travels through schist quartzite, while the later one originates in granite area where some functional but old gold mines are located. Freshly deposited sediments of river were collected upstream and downstream the industrial zone (East Singhbhum district). Samples were collected from four locations and analysed in <63 μm sediment fraction for heavy metals like Ni, Co and Cr by adsorption stripping voltammetry on hanging mercury drop electrode and Hg by anodic stripping voltammetry using polished rotating gold disk electrode. Enrichment of these metals over and above the local natural concentration level (NCL) has been calculated and applied to determine metal-pollution index (MPI) proposed by Goncalves et al. and also geo-accumulation index (Igeo) by Muller. Based on Muller’s classification, Ni, Cr and Hg have been classified from unpolluted to moderately polluted range in pre-monsoon period but for metals Ni and Cr, during the post-monsoon period the values have reached moderately polluted level while Hg has been classified under unpolluted to moderately polluted level except at the monitoring station situated upstream to Gurma Creek where it was found at unpolluted level. Presence of natural resources of the minerals is primarily the reason for their detection in river sediments (lithogenic) but some anthropogenic sources are also contributing for their presence at some sampling stations. Hg is considered to be chalcophilic in nature and is detected wherever known sulphidic ores of copper or nickel are present.

The Encyclopedia of igneous and metamorphic petrology

Abbreviations. Acid(ic) igneous rocks. Alkaline rocks-undersaturated. Alkaline rocks-undersaturated: other petrological terms. Alpine mafic magma stem. Alteration, replacement. Amphibolite. Amphibolite facies. Analcimite. Anatexis. Andesite and dacite. Andesite line. Anorthosite. Aplite. Appinite. Archaean volcanism. Ariegite. Assimilation. Astrobleme. Atoll garnet. Augitite. Aureole. Banding in igneous rocks. Basalt. Basic igneous rocks. Batholith. Breccia pipe. British Tertiary Volcanic Province. Brownstone facies. Buchite. Burial metamorphism. Bushveld Complex. Calc-alkaline rocks. Calderas and volcano-tectonic depressions. Carbonatite. Cataclastic rocks. Charnockite. Charnockite suite. Circum-Pacific plutonic and volcanic activity. Columnar jointing. Cone sheets. Contact (thermal) metamorphism. Contact metasomatism. Core. Cryptovolcanic structure. Cumulate textures. Depth zones. Deserpentinization. Diabase. Diapirism. Diatreme. Differentiation index. Diorite and tonalite. Dolerite. Double-diffusive convection. Durbachite. Dyke (dike). Eclogite. Eclogite facies. Element partitioning in petrogenesis. Emplacement-modes. Enclave. Endogenous dome. Epidote amphibolite facies. Eutectic melting. Experimental petrology. Explosive volcanic eruptions-classification. Facies of thermal metamorphism. Feldspathoidal rocks-genesis. Fenite. Flood basalt. Fluidization. Fumarole. Gabbro and norite. Geochemical modeling in petrogenesis. Geosynclinal volcanism. Geyser. Glaucophane schist facies. Gneiss. Granite. Granites and mineralization. Granites and volcanism. Granodiorite. Granophyre. Granulite. Granulite facies. Greenschist facies. Greenstone. Greisen. Harzburgite. Hauynitite. Hornfels. Hornfelsic textures. Hot ground. Hot spring. Hybridization. Hydrothermal processes. Hypabyssal rocks. Igneous intrusions-structural behavior. Igneous petrology. Igneous petrology - terms. Igneous rocks - classification and nomenclature. Igneous rocks - other terms. Igneous rocks - tectonic setting. Injection complex. Intermediate igneous rocks. Intrusion. Intrusion-layered. Intrusive igneous structures. Island arcs-petrology. Khondalite. Kimberlite. Laccolith. Lamproite. Lamprophyre. Latite. Lava and lava eruptions. Lawsonite-albite-chlorite facies. Leucitite. Lherzolite. Limburgite. Liquid immiscibility. Lopolith. Lunar petrology. Mafic and ultramafic inclusions in igneous rocks. Magma. Magmatic crystallization and paragenesis. Magmatic crystallization in metamorphic environments. Magmatic crystallization in open systems. Magmatic currents and flow. Magmatic differentiation. Magmatic-tectonic cycle. Marble. Mediterranean suite. Melilitite. Metamorphic convergence. Metamorphic facies. Metamorphic facies series. Metamorphic grade, metamorphic zone. Metamorphic mineral growth. Metamorphic petrology-use of thermodynamics. Metamorphic reactions. Metamorphic rock composition-graphical representation. Metamorphic rocks-other terms. Metamorphism. Metamorphism - controls. Metamorphism - processes. Metamorphism - types. Metasomatism. Meteorites - petrology. Mid-ocean ridge and ocean-floor petrology. Migmatite. Migmatite-origin of neosome. Migmatite-structural relationships. Mnemonics, acronyms. Mohorovicic discontinuity (Moho). Monzonite (syenodiorite). Nephelinite. Neutrality-pH and temperature variation. Noseanite. Nucleation of metamorphic minerals. Nucleation of minerals in magmas. Nuee ardente. Ocean-floor metamorphism. Ocean-island igneous rocks. Oceanic crust. Ophiolite. Orbicular rocks. Pacific and Atlantic suites. Paired metamorphic belts. Palaeovolcanology. Palagonite. Pegmatite. Pegmatitic ore deposits. Peralkaline igneous rocks. Peridotite. Petrochemical calculations. Petrographic methods. Petrographic microscope. Petrographic province. Petrological terms. Petrology-branches. Petrology-history. Phacolith. Phase rule. Phase transformation. Phenocryst. Phonolite. Phyllite. Picrite. Plutonic rocks. Plutonic rocks - classification and nomenclature. Pneumatolysis. Polymetamorphism. Polyphase metamorphic mineral growth. Porphyroblast. Porphyroclast. Porphyry. Prefixes, suffixes. Prehnite-pumpellyite facies. Ptygmatic vein. Pumpellyite-actinolite schist facies. Pyroclastic eruptions. Pyroclastic flows. Pyrolite. Pyrometamorphism. Pyrometasomatism. Pyroxenite. Rapakivi texture. Reaction principle and reaction series. Reaction rates in metamorphism. Reaction rim. Regional metamorphism. Retrograde metamorphism. Rheomorphism. Rhyolite. Rift valley volcanism. Ring dyke. Schist. Serpentinite. Serpentinization. Shock metamorphism. Silicate melting. Sill. Skaergaard intrusion. Skarn. Slate. Snowball garnet. Sodalitite. Solfatara. Sovite. Spilite. Spinifex texture. Statistics in petrology. Steinmann Trinity. Syenite. Tektite. Tephra. Tephrite, basanite. Textures of igneous rocks. Textures of metamorphic rocks. Thermal activity. Trachyandesite, trachybasalt. Trachyte. Trend surface analysis in petrology. Tuffisite. Ultrabasic igneous rocks. Ultramafic belts. Ultramafic lavas. Ultramafic rocks. Units and conversion factors. Upper mantle-experimental petrology. Volatiles. Volcanic breccia. Volcanic glass. Volcanic neck. Volcanic rocks. Volcanoes and volcanism. Water in rock melts. Xenolith. Zeolite facies.

Petrology and geochemistry of Mesozoic igneous rocks, Bükk Mountains, Hungary

Basic and ultrabasic igneous rocks of the Jurassic Szarvaskő complex (southwestern Bükk Mountains, NE Hungary) have previously been interpreted as dismembered fragments of a Mesozoic ophiolitic sequence comprising mainly gabbroic sills intruded into deep-water terrigenous shales. Abundant extrusive pillow basalts, layered ultramafics and plagiogranite bodies are also present. Gabbros and basalts showing slight LREE depletion ( Ce Yb N =0.84–0.93 ) and very slight negative Eu anomalies (0.92–0.98) are considered to be close to liquid compositions, while some gabbros with the lowest overall REE abundances and positive Eu anomalies ( Eu Eu ∗ = 1.14–1.29 ) are regarded as plagioclase+clinopyroxene cumulates. The REE characteristics of the most primitive rocks are very similar to those of N-type MORB. Differentiated magmas show negative Eu anomalies and increasing REE enrichment, consistent with fractionation of plagioclase and clinopyroxene. In most rocks from the Szarvaskő complex, strong enrichment is seen in Ba, Rb and K, compared with the values for MORB. Age-corrected ϵSr t -values of the Szarvaskő complex range from −0.2 (basic rocks) to + 36.4 (evolved rocks). The ϵNd t -values vary between +6.4 (basic rocks) and +3.3 (evolved rocks). The variation in ϵNd t is probably not due to alteration or metamorphism, since simple REE patterns indicate REE immobility, and is considered to be caused by contamination during magmatic fractionation. The high and variable ϵSr t -values could be due to transfer of radiogenic Sr from the surrounding sediments during very low-grade regional Alpine metamorphism. It is suggested that the basic magmas of the complex were probably originally MORB-like, but during evolution in a shallow magma chamber, they became contaminated by terrigenous sediments. The nearby Triassic Darnó Hill complex is much more strongly altered, does not show the same depletion in LREE, and has lower ϵNd t -values. It is considered to have been formed in a different tectonic setting, possibly a continental margin or oceanic island.

The clew bay group: A displaced terrane of highland border group rocks (Cambro‐ordovician) in Northwest Ireland

AbstractMarine turbidites, tuffs, black mudstones and conglomerates of the Cambro‐Ordovician Clew Bay Group, were deposited in the E–W elongate transtensional Clew Bay Graben that is centred on Clew Bay, NW Ireland. The group is characterized by extensive sedimentary deformation and mass movement on slides; olistostromes, autoclastic breccias and course proximal turbidites are interbedded with apparently less disturbed but often overturned sediments.The Clew Bay Group lies structurally above serpentinized dunite/harzburgite breccias, schistose carbonate peridotites, and other basic and ultrabasic igneous rocks that have ophiolitic geochemical affinities; the sediments may have been in part deposited upon oceanic crust. Ophiolites and sediments that now rest on the Clew Bay Thrust abut Silurian shallow water strata in which the main tectonothermal history, associated with sinistral transcurrent faulting along the thrust zone, is dated at about 410 Ma. The sole thrust dips northward and coalesces with a major deep structure along the Fair Head‐Clew Bay Line (FCL) that is the western continuation of the Highland Border Fault of Scotland. Blueschist relics in the Dalradian immediately to the north of the FCL indicate that subduction was active early in the history of the late Cambrian–early Ordovician Grampian orogeny. The Clew Bay Thrust was a sinistral, transpressional shear zone late in its history, but it probably originated as an obduction complex.The Clew Bay Group cannot be traced into sedimentary, metamorphic or structural continuity with the adjacent Dalradian to the north or Ordovician and Silurian rocks in the South Mayo Trough to the south. It should be considered as a distinct terrane (Clew bay Terrane) or a subterrane of Highland Border‐type rocks along the southern margin of the Grampian Terrane.

High-pressure metamorphism in metabasites from the Betic Cordilleras (S.E. Spain) and its evolution during the Alpine orogeny

The Nevado-Filabride complex is the lowest tectonic unit of the Betic Zone sensu stricto (ss) of the Betic Cordilleras (S.E. Spain). The upper series of this complex consists of a metamorphosed sequence intruded by basic and ultrabasic igneous rocks. High-pressure metamorphism in the eclogite and blueschist facies is recorded in the metabasites, but this was partially obliterated by further successive metamorphic stages in the almandine-amphibolite and greenschist facies.