Petrology and Geochemistry

Within the framework of the International Continental Drilling Program (ICDP) we propose a comprehensive initiative to drill the continental crust bordering modern and ancient convergent and collisional plate boundaries. These zones host the vast majority of modern megacities and industrial installations on Planet Earth, and at the same time are loci of major earthquakes , tsunamis, volcanic eruptions and other associated great natural threats to human life and to economies. In-depth understanding of dynamic Earthprocesses at convergent and collisional plate boundaries is not possible without scientific drilling embedded into integrated research programmes. The set of scientific questions identified here is rooted in the plate tec-tonic paradigm of a dynamic Earth. Proposed studies derived from these questions target on (1) the dynamics of active subduction and collision zones, with focus on the seismogenic zone at the plate interface, and the distribution of deformation and seismicity in general, (2) the role of mantle plumes in orogeny, (3) supra-subduction magmatism in arc systems, (4) the geological manifestation of deep subduction and exhumation of the lithosphere, and (5) aspects relating to continental birth and growth through Earth history. ICDP drilling in convergent and collisional plate margins faces unprecedented challenges regarding drilling technology, drilling depth and requirements for long-term monitoring of Earth processes in downhole observatories.

The Florida phosphate deposits in Four Corners and Hardee County mines are composed mainly of phosphate minerals and quartz in addition to subordinate proportions of feldspars, dolomite, calcite, gypsum, kaolinite, attapulgite and montmorillonite. These phosphorites contain three structurally different types of mudclasts: massive mudclasts, mudclasts with concentric structure and mudclasts consisting of agglomerates of apatite mi-croparticles. The latter are represented by particles resembling phosphatized fossil bacteria associated with microbial filaments, and hollow apatite particles having surfacial coatings and connected to microbial filaments. The Florida phosphate particles are reworked and vary in mineral composition, color and shape. They are composed of a mixture of well-crystalline species including carbonate fluorapatite (francolite), carbonate apatite and fluorapatite. The color variation of the phosphate particles is related to difference in mineral composition, extent of diagenetic effects and reworking. The light-colored mudclasts are characterized by the presence of carbonate apatite and aluminum hydroxide phosphate minerals, whereas the dark mudclasts are rich in iron aluminum hydroxide phosphate minerals. The Florida phosphorites are suggested to be formed partially by authigenetic precipitation, replacement of the sea floor carbonate and diatomite, and microbial processes. With respect to elemental geochemistry, the analyzed particles contain small percentages of sulfur and iron which are related to the occurrence of pyrite. Traces of silica and alumina are recorded which may be attributed to the diagenetic. Some of the tested particles are relatively rich in phosphorous, fluorine, calcium, and magnesium, while poor in silicon, potassium and sulfur. Whereas, the bioclasts (especially teeth) are relatively rich in calcium, phosphorous and fluorine while poor in silicon, aluminum, magnesium and potassium. Hence, the microchemical analyses revealed that differential dia-genesis affected mudclasts more than bioclasts. There is a complete compositional gradation between clay and phosphate particles which reflects their interaction. This involved kaolinitization of the phosphate particles, phosphatization of the clay mineral particles and production of silica.

Dibenzothiophene, phenanthrene, methyldibenzothiophene, methylphenanthrene, nickel and vanadium content,
have been determined in eight oil samples from different oil fields in the Central Gulf of Suez. These parameters are used
together to provide information on source organic matter input, depositional environment, and the maturity of oils. The results
showed that the crude oil samples are classified into moderately mature oil which include N. October, Belayim marine, Belayim
Land and July fields, generated in a strongly reducing (marine) environment, characterized by low wax content, moderate to
high sulfur, high concentrations of nickel and vanadium, and low nickel/vanadium ratios. Mature oils generated from source
rocks deposited in lacustrine palaeoenvironmental conditions and includes oils from Issaran, E Kareem, El-Khaligue and El Ayun
fields characterized by high wax, low sulfur, low quantities of metals, and have higher nickel/vanadium ratios.

The nature and geodynamic setting of Inner Makran ophiolites (SE Iran) are controversial and are the focus of a growing debate. The Fannuj-Maskutan ophiolite complex (central Inner Makran) is made up of lherzolites, harzburgites, layered and isotropic gabbros and diabase dikes and basaltic lavas. Here we present new textural description, mineral and whole-rock chemistry of peridotites together with bulk geochemistry of magmatic mafic rocks and U-Pb geochronology and Lu-Hf isotopes of inherited zircons in gabbros, with the aim to reconstruct the petrogenesis of the Fannuj-Maskutan ophiolite. The results indicate to a subduction-metasomatized depleted mantle source experienced 10-20% of partial melting. A transition from IAT-gabbros to E-MORB-basalts is also outlined. We interpret the obtained results as evidence for the Fannuj-Maskutan genesis in a supra-subduction zone (SSZ) basin developed in the Iranian cadomian crust as indicated by the presence of inherited Cadomian zircons (ca. 515 Ma, εHf (t) : −13.6-+11.2). Comparing the Fannuj-Maskutan ophiolites to well-known SSZ-systems such as the South Sandwich SSZ, and integrating with the existing literature on Inner Makran ophiolite belt we interpret the Fannuj-Maskutan ophiolite as a part of a major SSZ-basin opened in the Iranian cadomian crust and evolved during the Neotethys subduction under Central Iran.

The Iron Age societies of the southeastern Iberian Peninsula, like their Greek and Etruscan counterparts, used stone sculptures to decorate their sanctuaries and cemeteries. Limestone was the raw material used. While abundant throughout the region, it was not always of sufficient quality to implement the iconographic projects at hand. This paper describes a study of Jutia monument (fourth to second centuries BCE), an architectural structure supporting a number of zoomorphic sculptures. Located at a distance from any major city of the time, the sculptor’s workshop had to select the best materials in the surrounds. The present study aims to establish the origin of the limestone used and ascertain how decisions were made and collective work invested to build this monument. A geological study of the possible areas of origin is supplemented with the petrological characterisation of the respective outcropped materials and the archaeological elements recovered. Colour parameters, ultrasound pulse velocity (UPV) and limestone hardness and geochemical composition, the latter using a handheld XRF instrument, are also determined. The findings reveal that the figures were sculpted from Upper Miocene calcarenite or sandy limestones quarried at around 3 km from the site. In contrast, other parts of the building were erected with bioclastic limestone from the immediate surrounds, at just 200 m from the monument.

Garnet-(olivine) websterite xenoliths from the lithospheric mantle of the central and northeastern parts of the Siberian Craton contain exsolution microstructures after Si-and Ti-rich precursor garnets. We petrographically, geochemically, and thermobarometrically investigated 13 such xenoliths from the Mir, Obnazhennaya, and Udachnaya kimberlite pipes. All samples contain garnet grains with needle-to lamellae-shaped precipitates (up to 3.0 vol%), including Ti-oxide and/or pyroxene. Orthopyroxene and clinopyroxene grains host oriented lamellae of complementary Ca-rich and Ca-poor pyroxene, respectively, in addition to lamellae of garnet and Ti-and/or Cr-oxides. The common exsolution lamellae assemblages in garnet and pyroxene imply that exsolution occurred during cooling from high-temperature precursors. Exsolution is unlikely to have resulted from variations in pressure, given experimental and thermodynamic constraints. Host mineral partitioning of transition metal and lanthanide elements with different diffusivities record temperatures that range between those of local geotherms and a dry pyroxenite solidus. Inferred magmatic minimum temperatures of 1500-1700 °C satisfy the physical conditions predicted from experimental studies of the solubility of excess Si and Ti in garnet. Gran-ular inclusions of all major minerals within each other imply an overlapping crystallisation history. The reconstructed compositions of the websterite whole-rocks have high MgO contents (15.7-35.7 wt%). A plot of MgO/ SiO 2 versus SiO 2 forms an array, apart from the compositions of natural websterites that formed by interaction of peridotite with basaltic or siliceous melts. The array overlaps the compositional range of komatiite flows from Commondale and Barberton, South Africa, including spinifex, massive, and cumulate subtypes of komatiites. Other major and minor element abundances and ratios of the Siberian websterite suite resemble those of South African Al-enriched komatiites and are distinct from melt-rock reaction websterites. Therefore, the mineral mi-crostructures and geochemistry of the Siberian websterites are suggestive of the former presence of a thermal anomaly. We propose that mantle plume activity or a similar form of lower-mantle ascent played a major role in stabilising cratonic nuclei before amalgamation of the present-day Siberian Craton.

Jacques-Marie Bardintzeff (2021)
« Volcanologie », 6ème édition, Dunod

VOLCANOLOGIE, 6th edition, DUNOD, 2021, by Jacques-Marie BARDINTZEFF (jacques-marie.bardintzeff@universite_paris-saclay.fr).
This sixth edition, in French, is augmented and improved : 352 pages, 160 black and white photos, figures and tables, plus 16 extra pages of new colour photos, 650 references (numerous recent), web sites, glossary.
Chapters and paragraphs concerning supereruptions, planetary volcanoes, risks and mitigating, volcano and climate, are particularly rewritten and actualized. The price is 36 euros.
For more information, please contact: DUNOD, 11 rue Paul Bert CS 30024, 92247 Malakoff Cedex, France, phone: 33 1 41 23 66 00
ISBN 978-2-10-081914-0
1ère éd., Masson, 1991; 2e éd., Dunod, 1998, 3e éd., 2006, 4e éd., 2011, 5e éd., 2016; traduit en allemand, 1999; traduit et adapté en anglais / américain avec A.R. McBirney, 2000)


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https://www.dunod.com/sciences-techniques/volcanologie-2


La sixième édition de « Volcanologie » par Jacques-Marie Bardintzeff (jacques-marie.bardintzeff@universite-paris-saclay.fr) vient de paraître aux éditions Dunod. Cette nouvelle version est singulièrement augmentée et complétée : 352 pages, 160 photos, schémas et tableaux, 16 pages couleur hors texte.
Les chapitres et paragraphes consacrés aux super-éruptions, au volcanisme planétaire, aux risques et leurs prévisions, aux relations entre volcans et climats à l’échelle de la planète sont particulièrement remaniés et actualisés. 650 références bibliographiques (nombreuses récentes), un glossaire ainsi que des adresses de sites web sont annexés. Le prix de l'ouvrage est de 36 euros.
Pour les étudiants de Licence, de Master, des « prépas » Capes et Agrégation et tous les passionnés et curieux de volcans.
DUNOD, 11 rue Paul Bert CS 30024, 92247 Malakoff Cedex, 01 41 23 66 00
ISBN 978-2-10-081914-0

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This study utilizes the trace and rare earth element geochemistry of bulk ores and in situ LA-ICP-MS analyses of
mineral grains to clarify the controversy in the origin of the Bahariya sedimentary iron ores, Egypt. Different types
of iron ores were identified in the Bahariya Oasis including high grade, high-Mn, high-Ba, oolitic, and ochreous
iron ores. Hematite and goethite are the main constituents of the studied ores with some manganese oxide
and hydroxide minerals (pyrolusite, bixbyite, cryptomelane, aurorite, romanechite, manjiroite, and pyrochroite).
Barite is common in the high-Ba ore, while some quartz, calcite, and halite are detected in the oolitic iron ore.
High-Mn iron ores are characterized by higher contents of SiO2,Al2O3, MgO, CaO, Na2O, and K2O, while highBa iron ore has higher TiO2contents. Analyses of bulk ores and in situ mineral grains are characterized by substantially high contents of Ba (average of 9497 ppm); also Zn and Sr occur in considerably high concentrations
(averages of 4263 and 429 ppm, respectively). Mn-rich ores and Mn-bearing minerals show relative enrichments
of trace metals compared to the Mn-poor ores probably due to the ability of Mn-bearing minerals tofixsuchtrace
metals by adsorption, absorption, and/or replacement. TheΣREE ranges between 2.6 and 80 ppm with an average
of 23 ppm. High-Mn ores show higherΣREE (average of 61 ppm) compared with the low Mn ore (average of
13 ppm). The oolitic iron ore shows very lowΣREE content (7 ppm). Red and yellow ochers from El Gedida
mine have similarΣREE values (38 and 39 ppm, respectively), while red ocher from the Ghorabi area has relatively higherΣREE (57 ppm). Chondrite-normalized REE patterns of all types of iron ores, whether in the form of bulk
ores or Fe- and Mn-bearing grains, have LREE enrichment relative to HREE as shown by (La/Yb)Nratios that vary
from 1.7 to 29.4. Majority of the bulk samples and mineral grains have negative Eu anomalies with EuN/Eu*
ranges from 0.68 to 0.8. However, bulk samples of one high grade and high-Ba ores as well as some of the Mnbearing grains from El Gedida ores show positive Eu anomalies with Eu/Eu* ranges from 1.1 to 17.7. With few exceptions, all bulk ores and mineral grains show negative Ce anomalies with Ce/Ce* range from 0.28 to 0.96. A
seawater precipitation (hydrogenous to hydrothermal exhalite) is proposed for the Bahariya iron ores. The hydrogenous origin is suggested based on the occurrence of high-Mn iron ores in the base of the iron ore succession,
oolitic texture of some of these ores, Si–Al plot, low La/Ce ratios, high Y/Ho ratios, and LREE-enriched patterns
with negative Eu anomalies of most of the bulk ores and mineral grains. The hydrothermal contribution to the
source of these iron ores can be evident from the high contents of some trace elements such as Ba, Zn, and Mo,
and plots the analyzed samples in the hydrothermalfields of the Fe–M–(Ni + Co + Cu)∗10 ternary diagram,
(Co + Ni)–(As + Cu + Mo + Pb + V + Zn) and (Co + Ni + Cu–Co/Zn) binary plot, lowΣREE concentrations
and positive Eu anomalies and high La/Ce ratios in some of the analyzed samples. The hydrothermal contribution
looks for local effect and is restricted to El Gedida area

Minyak bumi adalah campuran kompleks hidrokarbon dan senyawa-senyawa organik lainnya. Komponen hidrokarbon adalah komponen yang paling banyak terkandung di dalam minyak bumi. Ada tiga faktor utama dalam pembentukan minyak bumi, yaitu: 1. Adanya batuan asal (source rock) yang secara geologis memungkinkan terjadinya pembentukan minyak bumi. 2. Adanya perpindahan (migrasi) hidrokarbon dari batuan asal menuju ke " batuan reservoir " (reservoir rock), umumnya batu pasir ataupun batugamping yang berpori-pori (porous) dan ukurannya cukup untuk menampung hidrokarbon tersebut. 3. Adanya jebakan (entrapment) geologis. Struktur geologi yang tidak teratur bentuknya, akibat pergerakan bumi misalnya gempa bumi dan erupsi gunung api serta erosi oleh air dan angin secara terus menerus, dapat menciptakan suatu " ruang " dibawah permukaan yang dapat menjadi jebakan hidrokarbon. Apabila jebakan ini dilingkupi oleh lapisan yang impermeable, maka hidrokarbon tadi akan diam di tempat dan tidak bisa bergerak kemana-mana lagi. Pencarian lain yang mirip dengan artikel ini : kimia minyak bumi, minyak bumi, pengertian minyak bumi, sifat kimia minyak bumi. Komposisi minyak bumi, jenis-jenis minyak bumi, komponen minyak bumi, makalah kimia minyak bumi, bahan pembentuk minyak bumi, makalah minyak bumi kimia, komponen-komponen minyak bumi. Minyak bumi yang belum diolah disebut minyak mentah (crude oil). Minyak mentah merupakan campuran yang kompleks, yang komponen terbesarnya adalah hidrokarbon. Komposisi Kimia penyusun minyak bumi diantaranya adalah sebagai berikut : 1. Senyawa hidrokarbon alifatik jenuh (Alkana), seperti isoooktana (2,2,4 trimetilpentana), n-oktana, dan sikloalkana (siklopentana dan sikloheksana). 2. Senyawa hidrokarbon aromatik, seperti benzena 3. Senyawa lain dalam jumlah kecil (mikro), seperti senyawa belerang, senyawa nitrogen, senyawa oksigen, dan senyawa organologam.

Two pairs of high-field-strength elements Nb–Ta and Zr–Hf. display contrasting behaviour during the evolution of a
peraluminous granitic pluton that is composed of leucomonzogranites and subordinate greisen-hosted topaz-bearing leucogranites. Zr and Hf progressively decrease with differentiation and their ratio remains the same, close to the chondritic value ~36. The crystallization of zircon which contains the bulk of these two elements in the rocks, does not modify the Zr/Hf ratio. With increasing differentiation, Nb and Ta show an increase accompanied by a distinct decrease of the Nb/Ta ratio from 14 in leucomonzogranites to 2 in leucogranites and greisens. Tantalum correlates positively with Rb, Li and F and is strongly enriched in the evolved rocks, implying that an addition of internally derived mineralizing fluids and fluid fractionation played a key role in the variation of the Nb/Ta ratio in rocks with K/Rb ratios -150. The values of the Nb/Ta ratio in the continental crust are typically lower than those of mantle and chondrites ~17.5. suggesting that fluid
fractionation might have been an important process during the evolution of the continental crust.

The petrographic and geochemical composition of the Dharla River sediments has been examined to infer their sediment type, degree of weathering, provenance, and tectonic settings. Petrographically the sediments are characterized by the high quartz content (64.97 to 74.24 wt%), followed by feldspar (7.04 to 15.20 wt%), mica (5.38 to 19.92 wt%), lithic fragment (3.46 to 8.14 wt%), and heavy minerals (1.98 to 6.94 wt%). Geochemical composition shows marked enrichment of SiO 2 (mean ~ 74.16%) and a strong negative correlation with the other major oxides because of quartz dilution. The Chemical index of alteration (CIA, 45.52 to 63.51); Plagioclase index of alteration (PIA, 43.13 to 66.55); W index (20.15 to 32.86) and Rb/Sr ratios (0.35 to 0.98) suggest low to moderate intensity of chemical weathering in the source area. Geochemical classifications of the studied samples show mostly litharenitic immature type of sediments also reflects high index of compositional variability (ICV, 0.96 to 1.72). The ternary diagrams of Al 2 O 3-(CaO + Na 2 O)-K 2 O (or A-CN-K) and of mafic rocks, felsic rocks and degree of weathering of the source rocks (or MFW) and several immobile trace element ratios (e.g. light rare earth element/heavy rare earth element or LREE

The H. L. Hunley, the world's first successful submarine which sank in 1864 offshore of Charleston, South Carolina, contains a number of rusticles identified on the interior of the hull during excavation. Rusticles are biologically mediated iron concretions that form on exposed iron in marine environments; within the Hunley they are generally one-half to two centimeters in diameter, two to six centimeters in length, and extend down from hull pertubations such as rivet heads, plate seams, and other metal objects. Petrographic observations made with fabricated polished thin sections in both normal and reflected light provide insights on the internal morphology of several rusticles in this preliminary investigation. Different internal regions of the rusticles were found to have different morphologic and chemical character. Chemical assays from SEM/EDS were used to characterize and map the elemental distributions in the rusticles. Different regions, as segregated by their morphology, were found to have different elemental concentrations. It was found that the elemental assemblage from the rusticles as observed in SEM/EDS included; O, Fe, C, Si, Zn, Ca, Cl, S, Mg, Al, Mn, Ti, K, and P. These chemical assays allow for comparison between rusticles collected and studied from other marine wrecks. XRD techniques have also been used to attempt characterization of the specific mineralogy of the generally amorphous samples. These rusticles may provide useful information as to the nature of their formation through time and the environment in which they formed.

This study was conducted in Zajaca, west of Serbia during the period of May 13th 2013 to January 20th 2014, analysing water of Stira River, to assess the impact of the factory on water quality. The samples of river water were taken upstream and downstream then acidified with HCl p.a., and analysed for the content of examined elements on ICP-MS. The results from ICP-MS analysis were compared upstream and downstream through t-Test in order to check if there’s significant difference. After this comparison it was found that the amount of metals (except barium, calcium and mercury), increased significantly in downstream due to the discharge of factory effluent. Hence, the results were compared with WHO guidelines to check if they are within established limit values.
In conclusion it was found that five elements namely: arsenic, cadmium, sodium, lead and antimony, had exceeded limit values thus, the water of Stira River is asserted to be contaminated by toxic elements.
Key words: river, downstream, upstream, factory, toxic elements, pollution/and contamination.

Sandur Manganese (mn) deposits belong to the
Sandur schist belt, of Dharwar Supergroup. The Sandur schist
belt is one of the important greenstone belts of the Karnataka
craton and is named after the town Sandur where it is typically
exposed. The rich manganese ore deposits associated with schist
belt have evoked the interest from very early times of economic
geologists, mining engineers and metallurgist. The Deogiri
formation comprises of orthoquartzites, dolomitic limestone,
mangenophyllite, metabasalt and meta grey wacke with
intercalated banded ferruginous chert. The Mn deposits of
Deogiri are known for its high grade Mn ores in our country.
The dominant ores are pyrolusite, psilomelane, braunite, nsutite,
cryptomelane and manganite. The Mn ore samples were
collected from different working blocks of mine from Deogiri
and SB halli, and were chemically analyzed for their major
constituents like MnO2, Fe2O3, MnO, SiO2, Al2O3, P2O5, CaO
and MgO. The bi-metallic ratio between Mn and Fe was
determined to determine the grade pattern of Mn ores in the
working blocks of Deogiri and SB halli. The Deogiri block bimetallic
ratio varies from 45.60 % to 59.50 % from the data it is
observed higher the bi-metallic ratio the concentration of Mn is
higher and lower the bi-metallic ratio lower the concentration of
Mn. In SB halli block the bi-metallic ratio ranges from 44.60 %
to 57.30 %. The same yardstick holds good for the SB halli block
also. The higher concentration of Mn is also controlled
structurally.

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.

Europium L III-edge X-ray absorption near edge structure (XANES) spectra were recorded for a series of synthetic glasses and melts equilibrated over a range of oxygen fugacities (fO 2 s, from −14 to +6 logarithmic units relative to the quartz–fayalite–magnetite, QFM, buffer) and temperatures (1250–1500 °C). Eu 3+ /ΣEu (where ΣEu = Eu 2+ + Eu 3+) values were determined from the spectra with a precision of ±0.015. Eu 3+ /ΣEu varies systematically with fO 2 from 0 to 1 over the range studied, increases with decreasing melt polymerisation and temperature , and can be described by the empirical equation:Eu 3þ =ΣEu ¼ 1 1þ10 −0:25 log f O 2 −6410=T−14:2Λþ10:1 , where Λ is the optical basicity of the melt and T is the temperature in K. Eu 3+ /ΣEu in glasses and melts equilibrated at the same conditions are in excellent agreement for Fe-free systems. For Fe-bearing compositions the reaction Eu 2+ + Fe 3+ = Eu 3+ + Fe 2+ occurs during quenching to a glass and the high temperature value of Eu 3+ /ΣEu is not preserved on cooling; in situ measurements are essential for determining Eu 3+ /ΣEu in natural melts.

Resume of my work:
The Rio Del Rey delta which represents the part of Cameroon’s margin situated at the North partof the Cameroon volcanic line, is the meeting point between three panafrican faults of the Benoue. . The South west part, wich is our study area, is still poorly known geologically and very little evaluated in terms of hydrocarbons at the internationals Scientific’s level. The main purpose here was to do an evaluation of petroleum potential of its SW side; with a 3D modeling under the software petrel.The seismic data were interpreted according to the method of seismic stratigraphy, which helped to highlight the growth fault, folds, discontinuities and different seismic facies. A quick-look of the well log data analysis allowed us to determine a lithological column consisting essentially of clays, silts and sands, highlight five reservoirs (S09, S1, S3, S4.1, S5f) of oils and gas. Hydrocarbon reserves were evaluated at 269.106sm3for oil, or around 1 billion 823 million barrels of oil for the reservoir S5F in our studied zone.

The objective of this study is to provide information on source organic matter input, depositional conditions and the correlation between crude oils recovered from Sunah oilfield and Upper Jurassic Madbi Formation. A suite of twenty-six crude oils from the Lower Cretaceous reservoirs (Qishn clastic) of the Masila Region (Eastern Yemen) were analysed and geochemically compared with extracts from source rock of the Upper Jurassic (Madbi Formation). The investigated biomarkers indicated that the Sunah oils were derived from mixed marine and terrigenous organic matter and deposited under suboxic conditions. This has been achieved from normal alkane and acyclic isoprenoids distributions, terpane and sterane biomarkers. These oils were also generated from source rock with a wide range of thermal maturity and ranging from early-mature to peak oil window. Based on molecular indicators of organic source input and depositional environment diagnostic biomarkers, one petroleum system operates in the Masila Region; this derived from Upper Jurassic Madbi organic-rich shales as source rock. Therefore, the hydrocarbon exploration processes should be focused on the known location of the Upper Jurassic Madbi strata for predicting the source kitchen.

The South-East Asian Tin Belt is one of the most tin-productive regions in the world. It comprises three north-south oriented granite provinces, of which the arc-related Eastern granite province and the collision-related Main Range granite province run across Thailand, Singapore, and Indonesia. These tin-producing granite provinces with different mineral assemblages are separated by Paleo-Tethyan sutures exposed in Thailand and Malaysia. The Eastern Province is usually characterised by granites with biotite ± hornblende. Main Range granites are sometimes characterised by the presence of biotite ± muscovite. However, the physical boundary between the two types of granite is not well-defined on the Indonesian Tin Islands, because the Paleo-Tethyan suture is not exposed on land there. Both hornblende-bearing (previously interpreted as I-type) and hornblende-barren (previously interpreted as S-type) granites are apparently randomly distributed on the Indonesian Tin Islands. Granites exposed on Bangka, the largest and southernmost Tin Island, no matter whether they are hornblende-bearing or hornblende-barren, are geochemically similar to Malaysian Main Range granites. The average ɛNd(t) value obtained from the granites from Bangka (average ɛNd(t) = -8.2) falls within the range of the Main Range Province (-9.6 to -5.4). These granites have SIMS zircon U-Pb ages of ca. 225 Ma and ca. 220 Ma, respectively that are both within the period of Main Range magmatism (~226-201 Ma) in the Peninsular Malaysia. We suggest that the granites exposed on Bangka represent the continuation of the Main Range Province, and that the Paleo-Tethyan suture lies to the east of the island.

High-K calc-alkaline granitoids exposed in Mubi area, northeastern Hawal massif forms an integral part of the well-exposed syn-to post-collisional plutons in eastern Nigeria. The evolution of the rocks can be linked to the thermo-tectonic period of faulting, uplift, cooling, fractionation, and high-level magmatism, which initiated granite intrusion and associated rocks during the Paleoproterozoic. A total of nine granitic rocks, constituting seven biotite granites of varying grain sizes and two porphyritic granites were sampled in Mubi area to shed new light regarding their petrochemistry. Detailed investigations indicate that the study area constitutes majorly Pan African granitoids. The massif has S-type strongly peraluminous geochemical signature, high-K calc-alkaline, magnesian, granodi-orite, exemplified by high ASI (averagely 0.81-1.59), low Na 2 O (average 2.09 wt. %), and CaO (average 2.37 wt%). More so, they exhibit low FeO t /(FeO t + MgO) ratios (0.64-0.80 wt%), low to moderate Na 2 O+K 2 O-CaO ratio (2.41-5.41 wt%), high Na 2 O+K 2 O (average 6.42 wt%), and K 2 O/Na 2 O ratios (average 2.11 wt%), as well as high Mg# (30.49-50.22), low molar CaO/(MgO + FeO t) (0.19-0.63 wt%), and molar Al 2 O 3 /(MgO + FeO t) ratio (2.10-4.31 wt%). Discrimination diagram shows that the granitoids are products of sedimentary protolith (metagreywacke) formed within a syn-collision and supra-crustal setting. The constituent mineral assemblages in the granitoids (quartz, plagioclase, alkali feldspar, bio-tite, hornblende, titanite, and iron oxides) from the northeastern Hawal massif are obviously related to the condition of evolution and compositions of the protolith. The manganese ore and associated minerals in the area are controlled by the N-S pegmatitic quartz, which is part of the Cameroon Volcanic Line. The manganese minerals are hydrothermally generated from rising thermal waters due to pressure decline and subsequent reactions with the crystalline igneous rocks, which consequently triggered the precipitation of manganese oxides of metallurgical grade (44.36-49.56 wt%) that can be further processed into desired metallic alloy to meet the required industrial standards. ARTICLE INFO

The idea of  the geology of Sri Lanaka was initially come from the morphology of  Sri Lankan terrain and peneplains concept. A peneplains is defined as a “Plain” produced by a long period of weathering and erosion. The geo morphology of sri lanka can best be described as three major peneplain as described by Frank Dawson Admas in 1929. The lowest peneplains surrounds the cental hill country in all side, and is a flat, sometimes gently undulating plain stretching to the cosat. It has as average height of less than 30m. But the rise around 90 m to 120m above sea level at the inland boundary .The middle peneplain rises from this inner edge of  the lower peneplain in a steep step of about 300m, and reaches a maximum elevation of 760m above sea level: it is best seen in the south and east of the island.Within it and rising from it in another steep step of 910m to 1200m is the highest peneplain at a general level of 1500 m to 1800m, but rising at some places up to 2100m to 2450m. The all three peneplains towards the south can best be viewed from Beragala junction in Haputhalaee. Adams thouth that the highest peneplain was the oldest of the three and that the island has been rising thought out its geological history in a slow vertical movement, exposing more and more land to atomospheric erosion and denudation.

Large, explosive, caldera-forming eruptions are amongst the most destructive phenomena on the planet, but the processes that allow the large bodies of crystal-poor silicic magma that feed them to assemble in the shallow crust are still poorly understood. Of particular interest is the timescales over which these reservoirs exist prior to eruption. Long storage times—up to 10^5 y—have previously been estimated using the repose times between eruptions and radiometric dating of crystals found within the eruptive products. However, more recent work modelling diffusion within single crystals has been used to argue that the reservoirs that feed even the largest eruptions are assembled over much shorter periods—10^1–10^2 y.

In order to address this question, I studied the >10 km3, 22-ka, dacitic Cape Riva eruption of Santorini, Greece. Over the ~18 ky preceding the Cape Riva eruption a series of dacitic lava dome and coulées were erupted, and these lavas are interspersed with occasional dacitic pumice fall deposits (the Therasia dome complex). These dacites have similar major element contents to the dacite that was erupted during the Cape Riva eruption, and have previously been described as “precursory leaks” from the growing Cape Riva magma reservoir. However, the Cape Riva magma is depleted in incompatible elements (such as K, Zr, La, Ce) relative to the Therasia magma, as are the plagioclase crystals in the respective magmas. This difference cannot be explained using shallow processes such as fractional crystallisation or crustal assimilation, which suggests that the Cape Riva and Therasia magmas are separate batches. Furthermore, there is evidence that the Therasia dacites were not fed from a long-lived, melt-dominated reservoir. There are non-systematic variations in melt composition, plagioclase rim compositions, and plagioclase textures throughout the sequence. In addition, high-temperature residence times of plagioclase and orthopyroxene crystals from the Therasia dacites estimated using diffusion chronometry are 10^1–10^2 y. This is short compared to the average time between eruptions (~1,500 y), which suggests the crystals in each lava grew only shortly before eruption. The different incompatible element contents of the Cape Riva and Therasia magmas and plagioclase crystals suggest that a new batch of incompatible-depleted silicic magma arrived in the shallow volcanic plumbing system shortly before the Cape Riva eruption. This influx must have taken place after the last Therasia eruption, which 40Ar/39Ar dates show occurred less than 2,800 ± 1,400 years before the Cape Riva eruption.

The rims of the plagioclase crystals found in the Cape Riva dacite are in equilibrium with a rhyodacite, with a similar composition to the Cape Riva glass. However, the major and trace element zoning patterns of the crystals record variations in the melt composition during their growth. The compositions at the centre of most crystals are the same as the rims; however, these crystals are often partially resorbed and overgrown by more calcic plagioclase. The plagioclase then grades normally back to rim compositions. This cycle is repeated up to three times. The tight relationships between the anorthite, Sr and Ti contents of the different zones suggests that the composition of the plagioclase crystals correlates with the composition of the melt from which they grew. The different plagioclase compositions correspond to dacitic and rhyodacitic melt compositions. The orthopyroxene crystals reveal a similar sequence, although they only record one cycle. These zoning patterns are interpreted to document the assembly of the Cape Riva reservoir in the shallow crust through the amalgamation of multiple batches of compositionally diverse magma. Models of magnesium diffusion in plagioclase and Fe–Mg interdiffusion in orthopyroxene suggest that this amalgamation took place within 10^1–10^2 y of the Cape Riva eruption.

Komatiites are ultramafic volcanic rocks that occur mainly in Archean and Paleoproterozoic greenstone belts. These olivine-rich rocks are assumed to have crystallized from magmas that
have about 28–30 wt % MgO. They are characterized by spinifex texture - platy or skeletal crystals of olivine set in a
glassy matrix. Chemically, komatiites resemble peridotites and have high MgO but low SiO2, TiO2 (<1 wt %), K2O (<0.5 wt %) and incompatible trace element contents. Most of their
compositional variations can be accounted for by olivine fractionation. Komatiites are conventionally considered
to be derived from high temperature melts that have eruption temperatures of about 1600oC and are produced by high degrees of anhydrous melting of mantle plumes. The abundance of Archean komatiites, their decrease through the Proterozoic and extreme rarity in the Phanerozoic have
been taken as evidence for secular cooling of the mantle. However, the plume model has recently been challenged.
In marked contrast, it has been proposed that komatiites originate via hydrous melting at a shallow depth in subduction environments at significantly lower melting temperatures than
those invoked by the plume hypothesis. This new model thus challenges traditional views of the early evolution of the Earth. Nevertheless, it appears that many komatiites are plume-related. In addition to the information they provide about the tectonics and the thermal evolution of Archean Earth,
komatiites are economically important because they host locally significant magmatic Ni-sulfide (Ni-Cu-PGE) mineralization.

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.

Genesis Perbukitan Gendol yang terletak di daerah Muntilan-Salam, menjadi hal yang menarik untuk dikaji karena menjadi pertentangan para ahli geologi. Sebagian ahli berpendapat bahwa genesis Perbukitan Gendol disebabkan oleh debris avalanche Gunungapi Merapi atau  normal faulting Perbukitan Menoreh, namun sebagian ahli yang lain membantah pendapat tersebut dan berpendapat lain bahwa genesis Perbukitan Gendol diakibatkan oleh vulkanisme purba insitu. Penelitian ini dilakukan untuk mengkaji lebih mendalam apakah genesis Perbukitan Gendol disebabkan oleh debris avalanche Gunungapi Merapi, normal faulting  Perbukitan Menoreh, atau vulkanisme purba insitu. Penelitian ini dilakukan dengan analisis karakteristik geologi Perbukitan Gendol. Hasil analisis
yang dipadukan dengan data-data sekunder dan penelitian sebelumnya menunjukkan bahwa genesis Perbukitan Gendol terbentuk oleh vulkanisme purba insitu. Hal tersebut didasarkan pada beberapa bukti. Bukti yang pertama adalah
litologi Perbukitan Gendol yang didominasi oleh lava yang terbentuk secara insitu dan adanya batuan intrusi dangkal. Bukti yang kedua adalah batuan beku penyusun Perbukitan Gendol yang khas berupa andesit basaltik - andesit,
Medium-K, yang mengandung klinopiroksen, ortopiroksen, dan hornblenda. Bukti yang ketiga adalah bentuk lembah-lembah Perbukitan Gendol yang menunjukkan kenampakan seperti kawah gunungapi dan distribusi bukit-bukit di Perbukitan
Gendol yang menunjukkan kelurusan pada arah tertentu. Kelurusan bukit-bukit tersebut mencirikan kelompok gunung api yang terbentuk pada sepanjang zona ekstensi.