Tschermak fractionation in calc-alkaline magmas: the Eocene Sabzevar volcanism (NE Iran)

Calc-alkaline arc magmatism at convergent plate margins is volumetrically dominated by metaluminous andesites. Many studies highlighted the importance of differentiation via fractionation processes of arc magmas, but only in the last decades, it has been demonstrated that not all rock-forming minerals may affect the evolution of calc-alkaline suites. In particular, a major role exerted by Al-rich hornblende amphibole as fractionating mineral phase has been documented in many volcanic arc settings. The aim of this work is to understand the role of the Tschermak molecule (CaAlAlSiO₆) hosted in the hornblende and plagioclase fractionation assemblage in driving magma differentiation in calc-alkaline magmatic suites. We explore this issue by applying replenishment–fractional crystallization (RFC) and rare earth element–Rayleigh fractional crystallization (REE-FC) modeling to the Sabzevar Eocene (ca. 45–47 Ma) calc-alkaline volcanism of NE Central Iran, where hornblende-controlled fractionation has been demonstrated. Major element mass balance modeling indicates RFC dominated by a fractionating assemblage made of Hbl_52.0–52.5 + Pl_44.1–44.2 + Ttn_3.3–3.9 (phases are expressed on total crystallized assemblage). REE-FC modeling shows, instead, a lower degree of fractionation with respect to RFC models that is interpreted as due to hornblende and plagioclase resorption by the residual melt. Calculations demonstrate that fractionation of the Tschermak molecule can readily produce dacite and rhyolite magmas starting from a calc-alkaline andesite source (FC = ca. 30 %). In particular, the Tschermak molecule controls both the heavy rare earth elements (HREE) and light rare earth element (LREE) budgets in calc-alkaline differentiation trends.     

Utilization of bituminous limestone ash from EL-LAJJUN area for engineering applications

The following work aims at minimizing the environmental impact of the solid wastes (ash) that is produced after the utilization of the bituminous limestone in thermal power stations and /or retort processes. Limy ash has been prepared from the El-Lajjun bituminous limestone by direct combustion at 1,200, 950, and 525°C respectively. The laboratory tests have been selected with respect to construction needs and possible post construction conditions. Utilization of the various types of ash in the stabilization problematic soils from Jordan as brown soils and the clayey marl has revealed optimum results. The unconfined compressive strength of the parent brown soil and the clayey marl has been raised from 5 kg/cm² to 50 and 25 kg/cm², respectively. The CBR value has been raised from 4.5 to 150% for both problematic soil types. Various mortars and construction elements can be produced at normal room curing temperature without the use of ordinary Portland cement (OPC). Low quality sub-base and base course can be mixed with ash to produce cement treated base (CTB) and roller compacted concrete (RCC) without OPC. Durable pavements, embankments can be constructed with very long life and low cost. CTB and RCC utilizing ash can be used in dam construction instead of normal soil in earth fill dams. The high alkalinity of El-Lajjun ash is considered as a disadvantage to be utilized in normal concrete mixes for structural purposes. Ash only can be mixed with aggregates to produce lean concrete like for blinding purposes to be prepared for foundation activities.     

Prediction of Blast-Induced Ground Vibration in a Mine Using Relevance Vector Regression Optimized by Metaheuristic Algorithms

Natural Resources Research - Prediction of ground vibration induced by blasting operations is a crucial challenge to engineers working in surface mines. This study aims to assess the efficiency of...     

Les granitoı̈des hercyniens post-collisionnels du Maroc oriental : une province magmatique calco-alcaline à shoshonitique

The post-collisional Hercynian granitoids crop out in the easternmost part of the Moroccan Hercynian belt. Petrographical and geochemical studies show a composition similarity in the various granitoids. The granitoids belong to per-aluminous and metaluminous magmatic associations. They have evolved according to a scheme similar to high-K calc-alkaline to shoshonitic associations. To cite this article: H. El Hadi et al., C. R. Geoscience 335 (2003).     

Preliminary studies on the primary production of north-west Persian Gulf during post-monsoon period

Primary productivity, chlorophyll-a and the euphotic zone depth were determined averagely as 161 mg C (m³ day)^–1, 3.48 mg m^–3 and 6.2 m, respectively, in the north-west Persian Gulf during the post monsoon period in 1975 and 1976.     

Characterization of natural hydrocarbon seepage in the South Caspian Sea off Iran using satellite SAR and geological data

Abstract

Two groups of oil slicks have been repeatedly detected in the Southern Caspian Sea, off Cape Sefidrud and close to the Iranian coast of the sea on the synthetic aperture radar (SAR) images acquired by the Sentinel-1A and Sentinel-1B satellites in April–June 2018. Analysis of the SAR images together with bathymetry, geological and geophysical data in geographic information system showed that these manifestations (oil slicks) visible on the sea surface have natural origin, related to the bottom seepage phenomenon and are associated with existing hydrocarbon system. Oil slicks are concentrated over the continental slope and related to local geological formations of the sedimentary cover having oil deposits related to paleo-delta of Sefidrud River. Our evidence shows that two seeps in this area are active and repeating. It is concluded that the SAR is an excellent tool for monitoring of seepage phenomenon. Moreover, results indicate that the use of remote methods to identify offshore natural oil seeps related to existing active petroleum system can be considered as a well-accepted approach to support oil and gas exploration in frontier areas such as the South Caspian Basin.     

Hydrographic network as a marker of Quaternary tectonics: the example of El Mencha River from the Kaous region,Jijel, Algeria

A river can be an excellent marker of Quaternary tectonics. This method is applied to the El Mencha River case study (Jijel), which is an active region of Northern Algeria. In the Kaous locality (wilaya of Jijel), El Mencha River shows, at some points of its course, a difference in the banks’ altitude and a sinuosity that contrasts with the gentle slope. The right bank is in a high position with respect to the left bank. Bank uplift is emphasized notably by the staging of the stepped alluvial terraces. The oldest of these terraces is found about 6 m from the current level of the riverbed. On the left bank, the floodplain is very flared, with traces of abandoned or immature channels. Prospecting by electrical imaging has highlighted (i) superficial resistant unstratified and lenticular fluvial layers above conductive stratified deposits; (ii) an abnormal contact between the resistant and the conductive layers interpreted as a NE-SW fault zone, and (iii) the evidence of filled paleovalley which manifests as a V-shaped incision in stratified deposits. Channel pattern adjustment involving a lateral migration of the riverbed and the uplifted alluvial terraces are a consequence of the fault activity during the Quaternary period.