List of articles (by subject) Geochemistry
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Open Access Article
1 - Biomarker application in the recognition of the geochemical characteristics of crude oils from the five depobelts of the Niger Delta basin, Nigeria
Timothy Anyanwu Bassey Ekpo Boniface OrijiBiomarker fingerprints of crude oils are useful indicators of origin of organic matter input in source rocks and depositional conditions which are useful indices for petroleum systems development within a hydrocarbon producing horizon. Twenty five (25) crude oil samples MoreBiomarker fingerprints of crude oils are useful indicators of origin of organic matter input in source rocks and depositional conditions which are useful indices for petroleum systems development within a hydrocarbon producing horizon. Twenty five (25) crude oil samples from the five depobelts of the Niger Delta basin, Nigeria were studied to describe their biomarker fingerprints, provide information on the origin of organic matter input in the source rock(s), determine depositional environmental conditions and thermal maturity of the crude oils. The study was based on biomarkers (steranes and hopanes), normal alkanes and acyclic isoprenoids (pristine and phytane) obtained from the gas chromatography–mass spectrometry (GC-MS) analyses performed on the saturated fractions of the crude oils. The results of pristine/phytane (Pr/Ph) ratios, Pr/n-C17 ratios, Ph/n-C18 ratios, C29/C27 sterane ratios, sterane/hopane ratios, %C27, %C28 and %C29 regular steranes, oleanane index, waxiness index, Ts/Tm ratios and Carbon Preference Index (CPI) values, indicated that the analyzed crude oils belong to the same family of oil and originated from terrigenous clastic source rock (s) containing land plant organic matter with minor marine organic matter input, deposited under oxic to sub-oxic paleoenvironmental conditions. The Pr/n-C17 versus Ph/n-C18 cross plot indicated marine algal type II and a mixed type II/III kerogen. The C32H:22S/(22S+22R) values together with Ts/(Ts + Tm), C29:20S/20S + 20R, oleanane index and CPI values indicated that most of the crude oils have reached thermal equilibrium with high thermal maturity levels. Manuscript profile -
Open Access Article
2 - Genesis and geochemical evolution of the Mio-Pliocene volcanic rocks in the SW of Bostanabad, NW Iran: A comparison with the classic Adakite
Farahd Pirmohammadi AlishahThe Sahand volcano (Kuh-e-Sahand) is located in NW Iran, about 60 km E of Lake Urumieh and 40 Km SSE of Tabriz. The volcano is a stratovolcano and is dominated by pyroclastic materials and lava flows in the Miocene-Quaternary. The Mio-Pliocene volcanic rocks are exposed MoreThe Sahand volcano (Kuh-e-Sahand) is located in NW Iran, about 60 km E of Lake Urumieh and 40 Km SSE of Tabriz. The volcano is a stratovolcano and is dominated by pyroclastic materials and lava flows in the Miocene-Quaternary. The Mio-Pliocene volcanic rocks are exposed in the Southwest of Bostanabad (Arvanehkuh, Biukdagh, and Ghapandagh masses) East-Azerbaijan province. These rocks formed a part of the Urumieh-Dokhtar Magmatic Belt (UDMB) and consist of andesites and dacites. The rocks display a porphyritic texture and contain phenocrysts of plagioclase, sanidine, amphibole, biotite, and quartz. Based on the geochemical data and multi-elemental pattern, these rocks are medium to high-K calc-alkaline suite and show Large-Ion Lithophile Elements (LILE) and Light Rare-Earth Elements (LREE) enriched normalized multi-elemental patterns, and Nb and Ti depleted. Chondrite-normalized REE patterns of the volcanic rocks display a decrease from LREE to Heavy Rare-Earth Elements (HREE) without any Eu anomaly, indicating their formation in a subduction zone in an active continental margin. They have higher SiO2, Sr content, Sr/Y, and La/Yb ratios and lower MgO, Y, and Yb contents compared to those of normal calc-alkaline volcanic rocks and show high SiO2 adakites (HSA). Based on geochemical data, the origin of these rocks is garnet-amphibolite with the residual phase of garnet and amphibole with a titanium phase. HREE and Y depleted patterns suggest the existence of garnet and amphibole as a residue in the source. The source of these rocks was probably garnet-amphibolite possibly generated during subduction of the Neo-Tethyan oceanic slab beneath the Central Iran zone and in fact, can be termed as classic adakite. Therefore, considering the importance of adakites in inferring continental geodynamic processes, it is recommended to pay attention to their discovery and identification with the help of various petrological and geochemical methods. Manuscript profile -
Open Access Article
3 - Geochemistry and diagenetic evidence of middle-late Permian deposits, Northern Iran
Alireza Chegini Iraj Maghfouri Moghaddam Mohamahosein Adabi Masoud LotfpourThis study provides a evaluation of the initial carbonate mineralogy, and diagenetic condition of the Ruteh Formation, a middle-late Permian carbonate sequence, in the Emarat section in Central Alborz, northern Iran. 200 samples were examined for petrographical contents MoreThis study provides a evaluation of the initial carbonate mineralogy, and diagenetic condition of the Ruteh Formation, a middle-late Permian carbonate sequence, in the Emarat section in Central Alborz, northern Iran. 200 samples were examined for petrographical contents and thirty-four samples were collected for geochemical analysis. The high Sr and Na contents, Sr/Na>1, and the presence of dolomites and dissolution fractures are indicative aragonite early mineralogy. The diagenetic process in the Ruteh Fm. are an indication of the marine, meteoric and burial diagenetic environments. The original carbonate texture in the Ruteh Fm. are Severely affected by diagenetic process. The data obtained from the values of the Major (Ca and Mg), minor (Sr, Na, Fe, and Mn), oxygen and carbone isotopes show the initial aragonite composition of the Ruteh Fm. deposited in a subtropical shallow water. An open diagenetic system was indicated by changes in the values of Sr / Ca and δ18O vs. Mn. The shallow burial diagenetic temperature of the Ruteh carbonate was approximate 28.6°C with the maximum diagenetic temperature of 53.4°C. Manuscript profile -
Open Access Article
4 - Separating geochemical anomalies by concentration- area, concentration-perimeter and concentration-number fractal models in Qaen region, East of Iran
Mahdi Safari Amir Haji Babaei Ali Daya Mahya ManouchehriniyaThe separation of geochemical anomalies from the background plays a pivotal role in geochemical exploration. Fractal and multifractal modeling of geochemical data has been recently used by numerous geoscientists. Three fractal methods were used to identify elemental geo MoreThe separation of geochemical anomalies from the background plays a pivotal role in geochemical exploration. Fractal and multifractal modeling of geochemical data has been recently used by numerous geoscientists. Three fractal methods were used to identify elemental geochemical anomalies in a case study from the east of the Qhaen region, southern Khorasan Province, East of Iran. These methods include concentration–area (C–A), concentration–perimeter (C–P), and concentration –number (C-N) methods. Copper mineralization occurs as vein and veinlet. Based on the analysis of heavy mineral samples, Cu contents are also observed in the southeastern, northern, and eastern parts of the Qhaen ore district, which are consistent with the results of the C–A fractal model and are genetically correlated with the andesitic unit. Indeed, after fieldwork and comparing the types of fractal models calculated, it can be concluded that the results obtained from the concentration-area method in this area were more efficient than other methods and are closer to reality. Manuscript profile -
Open Access Article
5 - Application of mineral chemistry in determining magma fertility of the Tarom northern and southern intrusions, NW Iran
Narges Yasami مجید قادری Seyed Hedayatalah Mousavi Motlagh Mir Ali Asghar MokhtariThe Tarom metallogenic belt of the Alborz magmatic belt in NW Iran is characterized by two alignments of intrusion in its northern and southern parts. The northern intrusion is younger than the southern one. Mineral chemistry investigations on the northern and southern MoreThe Tarom metallogenic belt of the Alborz magmatic belt in NW Iran is characterized by two alignments of intrusion in its northern and southern parts. The northern intrusion is younger than the southern one. Mineral chemistry investigations on the northern and southern intrusions characterize calc-alkaline magmatism. The northern intrusion consists mostly of quartz monzonite, and the southern intrusion comprises 1) gabbro - pyroxene quartz monzodiorite – quartz monzodiorite series and quartz syenite; 2) gabbro-diorite. Electron microprobe chemistries indicate that the northern plagioclases are An22 to An49 (oligoclase to labradorite). Plagioclases from the southern intrusion are An35 to An54 (andesine to labradorite) and gabbro-diorite plagioclases are An65 to An61 (labradorite). All pyroxenes correspond to the Quad (diopside, augite, and clinoenstatite) and crystallized at <2 to 5 kbar and H2O=10%. Formation temperatures of pyroxenes from the northern intrusion are in the range of 1100-1175°C. The northern feldspars show temperatures ~550°C. Formation temperatures for the clinopyroxene and feldspar from the southern intrusion are estimated at 1140-1185°C and 550-600°C, respectively. The Fe-rich biotite minerals from the northern intrusion suggest high oxygen fugacity magma. The northern and southern intrusions formed in an arc-related tectonic setting. The northern magma is sourced from the melting of a mixed mantle-crust in a subduction-related environment. The mineral composition of the northern intrusion implies magma fertility and porphyry mineralization which can be due to its high oxygen fugacity magma and lower crystallization pressure relative to those of the southern intrusion. Manuscript profile -
Open Access Article
6 - Evaluation and assessment of water and surficial sediments quality in Kebir-Rhumel Wadi, NE Algeria
Fouzia Hizir Abderrezak Krika Farès Kessasra Fouad KrikaThis study is to investigate the physico-chemical parameters and trace metal’s concentrations (Cd, Pb, Cu, and Zn) in water and surficial sediments (0-5 cm) samples in the Kebir-Rhumel Wadi, north-eastern Algeria. Trace metal concentrations was determined using fl MoreThis study is to investigate the physico-chemical parameters and trace metal’s concentrations (Cd, Pb, Cu, and Zn) in water and surficial sediments (0-5 cm) samples in the Kebir-Rhumel Wadi, north-eastern Algeria. Trace metal concentrations was determined using flame atomic absorption spectroscopy. The mean values of the physico-chemical parameters of the Wadi water samples are consistently above than thresholds of the Algerian standard. The comprehensive pollution index (CPI) varied from 1.46 to 3.90, indicating that the Wadi water was classified from polluted to seriously polluted. The eutrophication index (EIs) were above the unity, signifying that the eutrophication is serious, except for sites S1, S7, and S8. Metals was not detected in water samples. However, the metallic concentrations in the sediment were higher than background levels. The average geo-accumulation index (Igeo) revealed an order of trace metal contamination of the Kebir-Rhumel Wadi sediments: Pb>Cd>Zn>Cu. The contamination factor (CFs) of studied metals indicated a highly contaminated nature of sediments, whereas the Cd values indicated moderate contamination, considerable contamination with Pb and low contamination with Cu and Zn. The pollution load index (PLIs) were above the unity (1), displaying an advanced decline of the sediment’s quality. Potential ecological risk index of trace metals were changed as follows: Cd>Pb>Cu>Zn. Cadmium was of highly potential ecological risk to the ecological environment and prominently contribute to potential toxicity response. Manuscript profile -
Open Access Article
7 - Relationship between Rare Earth and Radioactive Elements
Seyyed Saeed Ghannadpour Ardashir HezarkhaniBased on the relation of radioactive and rare earth elements (REEs) in some of prospecting projects (particularly uranium prospecting) in central Iran, in current study, sampling from the Baghak anomaly in Sangan iron ore mine has been done according to radioactivity fo MoreBased on the relation of radioactive and rare earth elements (REEs) in some of prospecting projects (particularly uranium prospecting) in central Iran, in current study, sampling from the Baghak anomaly in Sangan iron ore mine has been done according to radioactivity for the first time. The purpose of this research is to survey such a relation in a different case study (skarn mine) with central Iran. Optical microscopic and scanning electronic microscopic (SEM) studies along with geochemical and statistical analyses (based on the spider diagrams) are employed. The significant amount of uranium, cerium, lanthanum and high a concentration of REEs in results, along with high amount of iron, is one of the reasons why Baghak anomaly is considered very important. Results show the accumulation of cerium in the allanite lattice (as the solid solution). Manuscript profile