Stress field and pore pressure analyses using geometric investigation of gypsum veins in the Naft Sefid oil field anticline, SW Iran
Subject Areas : Geoscience Fields in relation with Petroleum Geology
1 - Associate professor, Faculty of Earth science, Shahid Chamran University of Ahvaz, Ahvaz, Iran
Keywords: Gypsum veins, Pore pressure, Stress field, Naft Sefid Anticline, Gachsaran Formation, Zagros Fold-Thrust Belt,
Abstract :
In this study, gypsum veins occurring within the Gachsaran Formation of the Naft Sefid Anticline were employed as structural indicators to determine the orientation of the principal stress axes and to estimate the relative magnitudes of the principal stresses and pore pressure. For this purpose, Stereographic analysis of the veins pole data and Mohr diagram construction were performed. The results indicate that the wide dispersion of gypsum vein poles reflects the dominance of pore pressure over the mean stress (Pf > σ₂) during vein formation. Structural analysis revealed that the maximum principal stress axis (σ₁) trends northwest–southeast, consistent with the general compressional regime of the Zagros fold-and-thrust belt. The calculated driving pressure ratio (R′) ranges between 0.73 and 0.84, and pore pressure values vary from 4004 to 4571 units. The stress ratio (Ø = 0.81) indicating three axial oblate shape of stress ellipsoid during the development of gypsum veins. These results highlight the significant influence of stress field orientation and fluid pressure on vein development within the Gachsaran Formation.
[1] ALAVI, M., 2007. Structures of the zagros fold-thrust belt in Iran. American Journal of Science, 307, 1064–1095.
[2] ANGELIER, J., 1984. Tectonic analysis of fault slip data sets. Journal of Geophysics Researches, 89, 5835–5848.
[3] BEAR, G., BEYTH, M., RECHES, Z., 1994. Dike emplaced into fractured basement, Timna Igneous Complex, Israel. Journal of Geophysics Researches, 99, 24039–24051.
[4] BERBERIAN, M., 1995. Master ‘blind’ thrust faults hidden under the Zagros folds: active basement tectonics and surface morphotectonics. Tectonophysics, 241, 193–224.
[5] BERBERIAN, M., KING, G.C.P., 1981. Towards a paleogeography and tectonic evolution of Iran. Canadian Journal of Earth Sciences, 18, 210–265.
[6] BLANCE, E.J.P., ALLEN, M.B., INGER, S., HASSANI, H., 2003. Structural styles in the Zagros Simple Folded Zone, Iran. Journal of the Geological Society, 160, 401–412. doi:10.1144/0016-764902-110.
[7] BORDENAVE, M. L., HEGRE, J. A., 2005. The influence of tectonics on the entrapment of oil in the Dezful Embayment, Zagros Foldbelt, Iran. Journal of Petroleum Geology, 28(4), 339–368.
[8] FAGHIH, A., DEHGHAN M., SOBHANI S.S., 2023. Study of deformation pattern and kinematic characteristics in the Gelmandeh metamorphic complex, Saghand region, Central Iran. Advanced Applied Geology, 12(4), 617–634.
[9] FALCON, N.L., 1974. Problems of the relationship between surface structures and deep displacements illustrated by the Zagros range. Geological Society of London. Special Publication, 3, 9–22.
[10] FERGOSSON, C., NUTMAN, A., MOHAJJEL, M., BENNETT, V.C., 2016. The Sanandaj–Sirjan Zone in the Neo-Tethyan suture, western Iran: Zircon U–Pb evidence of late Paleozoic rifting of northern Gondwana and mid-Jurassic orogenesis. Gondwana Research, 58, 216–238.
[11] FOSSEN, H., 2016. Structural geology (2nd ed.). Cambridge University Press
[12] JOLLY, R.J.H., SANDERSON, D.J., 1997. A Mohr circle reconstruction for the opening of a pre-existing fracture. Journal of Structural Geology, 19, 887–892.
[13] KESHAVARZ, S., FAGHIH, A., ASADI, S., SOLEIMANI, M., ZAREI, S., 2024. PT conditions of deformation of the Gol-e-Gohar shear zone, SW Iran: Insights from analysis of quartz c-axis fabrics, recrystallization mechanisms and syndeformational fluid inclusions. Journal of Asian Earth Sciences, 262, 106010.
[14] KRUHL, J.H., 1998. Reply: prism- and basal-plane parallel subgrain boundaries in quartz: a microstructural geothermobarometer. Journal of Metamorphic Geology, 16, 142–146.
[15] LAW, R.D., 1990. Crystallographic fabrics. A selective review of their applications to research in structural geology. In: Knipe, R.J., Rutter, E.H. (Eds.), Deformation Mechanisms, Rheology and Tectonics. Geological Society of London, Special Publication No. 54, pp. 335–52.
[16] LAW, R.D., SEARLE, M.P., SIMPSON, R.L., 2004. Strain, deformation temperatures and vorticity of flow at the top of the Greater Himalayan Slab, Everest Massif. Tibet. Journal of Geological Society, London, 161, 305–320.
[17] MCKEAGNEY, C.J., BOULTER, C.A., JOLLY, R.J.H., FOSTER, R.P., 2004. 3D Mohr Circle analysis of vein opening, Indrama lode-gold deposit, Zimbabwe: implication for exploration. Journal of Structural Geology, 26, 1275–1291.
[18] MCQUARRIE, N., 2004. Crustal scale geometry of the Zagros fold–thrust belt, Iran. Journal of Structural Geology, 26, 519–535.
[19] MOHAJJEL, M., FERGUSSON, C.L., 2000. Dextral transpression in Late Cretaceous continental collision, Sanandaj–Sirjan Zone, western Iran. Journal of Structural Geology, 22, 1125–1139.
[20] NÜCHTER, J.A., STÖCKHERT, B., 2008. Coupled stress and pore fluid pressure changes in the middle crust: Vein record of coseismic loading and postseismic stress relaxation. Tectonics, 27, 1–23.
[21] OTSUBO, M., MIYAKAWA, A., KAWASAKI, R., SATO, K., YAMAGUCHI, A., KIMURA, A., 2016. Variations in stress and driving pore fluid pressure ratio using vein orientations along megasplay faults: Example from the Nobeoka Thrust, Southwest Japan. Island Arc, 25, 421–432.
[22] SADEGHI, S., YASSAGHI, A., 2016. Spatial evolution of Zagros collision zone in Kurdistan, NW Iran: Constraints on Arabia–Eurasia oblique convergence. Solid Earth, 7, 659–672. doi:10.5194/se-7-659-2016.
[23] SAEDI, G., SOLEIMANI, B., SAMANI, B., ARZANI, A., 2022. The interaction between faults and in-situ stress on the kinematic and subsurface natural fracture of Aghajari oilfield in southwest of Iran. Journal of Petroleum Science and Engineering, 208, 109567.
[24] SAMANI, B., 2017. Deformation flow analysis and symmetry of Goushti shear zone, Sanandaj-Sirjan metamorphic belt, Iran. Geopersia, 7, 117-130.
[25] SARKARINEJAD, K., AZIZI, A., 2008. Slip partitioning and inclined dextral transpression along the Zagros Thrust System, Iran. Journal of Structural Geology, 30, 116–136.
[26] SARKARINEJAD, K., KESHAVARZ, S., FAFGIH, A., SAMANI, B., 2017. Kinematic analysis of rock flow and deformation temperature of the Sirjan thrust sheet, Zagros Orogen, Iran. Geological Magazine, 154, 147–165.
[27] SCHWARZHANS, W., Bosold, A., JULAPOUR, A., ASHRAFZADEH, A.R., EHSANI, S.M., 2025. The structural geology of the High Central Zagros revisited (Iran) Available to Purchase. Petroleum Geoscience (2005) 11 (3): 225–238.
[28] SEMBRONI, A., Riccardo REITANO, A., FACCENNA, C., CALLIERI, P, 2024. The geologic configuration of the Zagros Fold and Thrust Belt: an overview. Mediterranean Geoscience Reviews, 6:61–86
[29] SEPEHR, M., COSGROVE, J., MOINEI, M., 2006. The impact of cover rock rheology on the style of folding in the Zagros fold-thrust belt. Tectonophysics, 427(1-4), 265-281.
[30] STOCKLIN, J., 1968. Structural history and tectonics of Iran, a review, A. A. P. G. Bull., 52(7), 1229-1258.
[31] TAKIN, M., 1972. Iranian geology and continental drift in the Middle East. Nature, 235, 147-150.
[32] TALEBIAN, M., JACKSON, J., 2004. A reappraisal of earthquake focal mechanisms and active shortening in the Zagros mountains of Iran. Geophysics, 156, 506–526.
[33] WILSON, C.J.L., ROBINSON, J.A., DUGDALE, A.L., 2008. Quartz vein fabrics coupled to elevated fluid pressures in the Stawell gold deposit, south-eastern Australia. Mineralium Deposita, 44(2):245-263.
[34] ZAMANI, B.G, 2023. Geodynamics and tectonic stress model for the Zagros fold–thrust belt and classification of tectonic stress regimes. Marine and Petroleum Geology, 155, 1-17.
