We present new petrographic and mineral–chemical data on the Antarctic EL3 enstatite chondrite Elephant Moraine 90299 (EET 90299), obtained by optical microscopy, scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and electron microprobe analysis (EMPA-WDS). EET 90299 preserves well-defined chondrule textures—barred pyroxene, radial pyroxene, porphyritic olivine–pyroxene (POP), and layered chondrules—together with brecciated clasts, showing substantial preservation of chondrule microstructures. The silicate assemblage is dominated by highly magnesian low-Ca pyroxene (Fs 0.7–2.1 mol%). Rare olivine crystals—average Fa 0.33 mol%—found in a POP chondrule are reported for the first time in EET 90299. Chondrule mesostasis shows compositional variability, from predominantly Na–Al and Si-rich to Ca-Na-Al, documenting chemical heterogeneity at the chondrule scale. A euhedral plagioclase crystal identified outside a chondrule displays heterogeneous Na–Ca distribution. The opaque phases comprise kamacite, schreibersite, alabandite, and troilite showing variable Cr contents (2.84 ± 1.07 wt%). The presence of metal–sulphide–silicate intergrowths (MSSI) whose origin remains ambiguous, indicates highly reduced conditions. Opaque-filled micro-veinlets and a wider opaque-rich vein document localized brittle deformation and concentration/redistribution of opaque phases, without pervasively disturbing the primary chondritic texture. Overall, EET 90299 documents the coexistence of well-preserved unequilibrated textures and localized secondary features, providing new micro-scale insights into EL3 chondrite evolution.
Predicting fracture architecture away from wells remains a major challenge in crystalline basement reservoirs because hydrocarbon storage and fluid flow are controlled predominantly by heterogeneous secondary fracture networks. This study evaluates whether an exposed granitoid block can provide a useful structural analogue for a deeply buried fractured-basement reservoir through integration of field fracture mapping at Ke Ga, borehole image and conventional well-log data from Well BH-415 in the Bach Ho field, multi-mineral petrophysical modelling, and seismic attributes in the Cuu Long Basin, offshore Vietnam. Three principal fracture populations were identified at Ke Ga, dominated by a NNE–SSW-oriented set striking approximately 20–30° and representing about 57% of the mapped fractures. The BH-415 basement contains vertically variable NNW–SSE, NNE–SSW, NE–SW, and NW–SE fracture trends associated with contrasting degrees of brecciation, alteration, and secondary pore development. The highest-quality fractured intervals exhibit net secondary porosity of up to approximately 6.6% and net permeability exceeding 1100 mD. Cross-scale comparison reveals partial rather than one-to-one structural correspondence: the dominant NNE–SSW Ke Ga population is compatible with NNE–SSW to NE–SW trends in BH-415, and a NW–SE population occurs in both datasets, whereas other subsurface fracture trends lack clear outcrop equivalents. RAI-derived seismic attributes further show spatial consistency with structurally heterogeneous intervals identified at the well. These results demonstrate that fracture orientation alone is insufficient to predict reservoir quality and that outcrop observations should be used primarily to constrain plausible structural architectures rather than to transfer petrophysical properties directly to the subsurface. The integrated workflow provides a conservative cross-scale framework for characterizing heterogeneous fractured crystalline basement reservoirs and evaluating the applicability of surface structural analogues in subsurface exploration.
The Jabal Sayid metavolcanic succession in the western Arabian Shield records Neoproterozoic arc magmatism and hosts a major VMS Cu-Zn-Au deposit in Saudi Arabia. This study investigates 31 volcanic samples, ranging from basalt to rhyolite, using petrography and whole-rock geochemistry to evaluate their petrogenesis, evolution, tectonic setting and metallogenic significance. The studied rocks belong to a subalkaline, calc-alkaline suite and show geochemical features typical of a subduction-related volcanic arc, including LREE enrichment, negative Eu and Nb anomalies, and LILE enrichment. Magma evolution was primarily controlled by the fractional crystallization of amphibole, clinopyroxene, plagioclase, and Fe–Ti oxides, although potential contributions from crustal interaction and/or crustal partial melting cannot be excluded. Widespread chloritic, sericitic, silicic, epidotic, and carbonate alteration reflects prolonged hydrothermal activity associated with felsic volcanism and favorable for VMS mineralization. These outcomes indicate that the Jabal Sayid succession formed within a juvenile Neoproterozoic volcanic arc and provide useful geochemical indicators for VMS exploration across the Arabian-Nubian Shield.
Borehole Ground-penetrating radar (GPR) is a promising technique for high-resolution geophysical imaging; however, water present in the borehole significantly affects electromagnetic (EM) waves, reducing imaging depth and resolution. Displacing borehole water with an EM-compatible imaging fluid improves borehole GPR performance. The fluid is developed and optimized through comprehensive compositional, electromagnetic, rheological, and numerical investigations. The fluid consisted of canola oil as the base fluid, stearic acid as the suspension stabilizer, and barite as the weighting agent. Barite sources and particle sizes, preparation procedures, and fluid properties were evaluated. Finite-difference time-domain (FDTD) simulations in gprMax compared air-, water-, and EM-fluid-filled boreholes using a 500 MHz source and reflections from a quartz vein and a perfect electric conductor (PEC) cylinder. The results demonstrated that a high-purity and micro-sized barite powder improved suspension stability and electromagnetic compatibility, while the oven-assisted preparation method produced the most stable formulations. Rheological analysis showed that the Herschel–Bulkley and Robertson–Stiff models provided the best agreement with experimental data. In the simulations, the water-filled borehole reduced quartz-vein and PEC-cylinder reflection amplitudes to 12% and 13% of their respective air-filled values, whereas the imaging-fluid-filled borehole produced amplitudes of 108% and 107%, respectively. Laboratory experiments demonstrated that the imaging fluid preserved electromagnetic wave propagation characteristics and improved target detectability compared with water-filled boreholes. These results support further evaluation of the imaging fluid for improving target detectability in borehole GPR investigations.
This study combines Raman Spectroscopy on Carbonaceous Matter (RSCM) thermometry and 40Ar/39Ar dating to constrain the thermal structure of the Variscan Para-autochthonous Unit (PAU) in the southern French Massif Central. The RSCM data define a regionally uniform peak-thermal pattern at TRSCM = 535 ± 50 °C throughout much of the PAU that coincides with P-T thermodynamic modeling of Grt-bearing metapelite indicating 525 ± 20 °C and 0.45 ± 0.05 GPa. This pattern post-dates thickening. No RSCM temperature increase can be seen around late granitic plutons, presumably as a consequence of unfavorable transformation kinetics. In contrast, 40Ar/39Ar step-heating dating of syn- and post-folial muscovite and biotite populations record regional N-S variations from 330 Ma to 325 Ma, down to 305 Ma around plutons. In pluton contact aureoles, 40Ar/39Ar systematics appear controlled by synkinematic recrystallization at 315–300 Ma, indicating a continuum of P-T variations during pluton emplacement. Older biotite and muscovite ages at 325 Ma record an early deformation stage predating regional muscovite ages between 320 and 315 Ma. In the eastern PAU, 332–322 Ma ages argue for an early thickening event. The decoupling between regional 40Ar/39Ar variations and the RSCM temperature record indicates that the thermal regime was associated with a late-thickening thermal event.
