Tectonics
Zahra Tavazo; Ebrahim Gholami; Hossien Motamedi; Bahman Soleimany
Abstract
Numerous mechanisms are active during folding in folded-thrust belts, such as the role of salt movement, the role of multiple detachments in sedimentary cover, interference between different phases of deformation, and the role of basement during folding. The performance of these mechanisms plays an important ...
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Numerous mechanisms are active during folding in folded-thrust belts, such as the role of salt movement, the role of multiple detachments in sedimentary cover, interference between different phases of deformation, and the role of basement during folding. The performance of these mechanisms plays an important role in the formation of different structures and geological features in geological units and folds geometry. In this research, such structures have been introduced and studied in Takhteh, Nahreh and Kuh-e-Lar anticlines in the north of Fars Paleo-High during field observations and measurement of geometric features of anticlines such as Aspect ratio, axial distance and half wavelength. These structures mainly include growth strata, geometry of tectonic synchronous strata, structures associated with shallow detachment such as rabbit ear structures, faults that are themselves structures that control the geometry and kinematics of structures, and sulfur springs that related to faults and rheology of exposed formations. The present study shows that the anticlines have an aspect ratio less than ten and are part of the detachment folds in which the detachment horizons have played a role and have a dextral arrangement. The formation of these anticlines occurred at the same time, which will be connected to each other, and these anticlines are associated with basement faults. The location of these anticlines is suitable for the presence of hydrocarbons but the basement fault in the southern flank of Takhteh anticline may affect the reservoir. The presence of water gaps and wind gaps in the region is a sign of uplift and activity of the region.
Y Jalili; M.M Khatib; E Gholami; M.R Ghassemi
Abstract
The Chelounak area in northwest of Birjand located in the Sistan suture zone extremity with middle-upper Eocene sedimentary and pyroclastic rocks, folded with different axes and exposed between the Chahak-mosavieh and Mohammadieh-Hessarsangi faults. These folds have a dominant characteristic of the dispersion ...
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The Chelounak area in northwest of Birjand located in the Sistan suture zone extremity with middle-upper Eocene sedimentary and pyroclastic rocks, folded with different axes and exposed between the Chahak-mosavieh and Mohammadieh-Hessarsangi faults. These folds have a dominant characteristic of the dispersion axis trends of NE-SW, NW-SE, and N-S. Geometric-Kinematic Analysis of these folds was carried out by data that taken from the structural interpretations, satellite images, geological maps, structural cross sections and mathematical functions. Aspect ratio, percent shortenings and the rotation folds axes are respectively for folds with NE-SW axis, 0.356-1.6, 20-77% and 28-40°; for folds with NW-SE axes0.352-0.620, 25-41% and 25-40°; and for folds with N-S axes 0.352, 25% and 24°. In this analysis the Chahak and Chelounak synclines and the Chahak anticline with NE-SW axis have maximum shortening and the Shavangan syncline with NW-SE axis has minimum shortening. This Study demonstrated the aspect ratio rises with increasing of shortening. Analysis of the structural elements demonstrates axis change of the Chelounak, Chahak and Hoj noj synclines and the Chahak and Chelounak anticlines with NE-SW Dominant axes affected by the Chahak-Mosavieh fault (~N-S trend) as well as the axis change of the Taj kouh, Shavangan and Hessar sangi synclines with NW-SE dominant axes affected by the Mohammadieh-Hessar sangi fault (~N-S trend). Dispersion of folds axial respect to compressive component has caused difference in aspect ratio, shortening and rotation of fold axes values.
R. Deevsalar; M.V. Valizadeh
Abstract
The results of field studies (i.e. shape, dimensions, spatial distribution, condition of enclaves and xenoliths in the host rocks at available outcrops) experimental observations (i.e. petrographical and microstructural study of enclaves and xenoliths and whole rock geochemistry of magmatic encalves) ...
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The results of field studies (i.e. shape, dimensions, spatial distribution, condition of enclaves and xenoliths in the host rocks at available outcrops) experimental observations (i.e. petrographical and microstructural study of enclaves and xenoliths and whole rock geochemistry of magmatic encalves) show that magmatic enclaves are mafic and felsic types, while xenoliths are hornfelsic. Elongation of magmatic enclaves and hornfelsic xenoliths along their apparent longitude axis in the margin of intrusive body are attributed to influence of stress on enclaves in melt or semi-solid phases and xenoliths in plastic form. In addition, this is related to impact of high force of magmatic flow in contact with metamorphic wall rocks. This indicates that the origin of xenoliths is the metamorphic rocks which lie at the periphery of the intrusive body. Existing of aligned mafic enclaves in the host, in addition to, presence of signs of plastic deformations (in microscopic scale) in micro-scale fluid features can be attributed to superimposition of solid-state deformation on magmatic flow. Due to lack of solid-state plastic deformation evidences, applicability of magmatic flow criteria and distinguishable interface of magmatic enclaves with host rocks in microscopic and macroscopic scales, spherical, globular, ellipsoidal and spindle shapes of mafic magmatic enclaves attributed to presence of theirs as mafic globule and packets in the host felsic magma, and also their similarity in superficial appearance, textural, mineralogy and geochemistry with the host rock, attributed to their different origin and magma mixing event. The formation of irregular shaped magmatic felsic enclaves with recognizable mineralogical and geochemical similarity to the host rocks, which are observed at the periphery or ceiling of the plutons, related to peripheral interruption in the primary phase of magmatic injection caused by the high pressure of consecutive injection pulse and replacement of new magmatic charge.
