Southern Limb Research Articles

Distribution of siderophile elements during sulphide fractionation within magmatic Ni-Cu-PGE systems: A LA-ICP-MS investigation of the Crystal Lake Intrusion, 1.1 Ga Midcontinent rift

Within the magmatic pyrrhotite-pentlandite-chalcopyrite assemblage, which is ubiquitous of many Ni-Cu-PGE deposits, the spatial distribution of PGEs and semi-metals during both sulphide fractionation and low temperature alteration is not well documented. In-situ characterisation of sulphides provides a mechanism to trace the behaviour of elements during ore formation, with trace element distribution patterns providing valuable insights at the microscale into the genesis of magmatic sulphide deposits. Here we report trace element data determined by quantitative LA-ICP-MS mapping for a suite of variably altered samples from the taxitic rocks of the undeformed Crystal Lake Intrusion, within the 1.1 Ga Midcontinent Rift. Combining LA-ICP-MS data with detailed petrography and multivariate statistics helps identity the processes responsible for elevated metal concentrations and observed trace element distribution patterns within Ni-Cu-PGE systems. Such data can also improve our understanding of the effects fluid interaction and assimilation of volatile rich rocks has on the metal contents of sulphides.Element maps reveal complex distribution patterns throughout the disseminated sulphides of the Crystal Lake Intrusion, which are notably enriched in Pd relative to the massive sulphides developed locally along the basal contact. Replacement of the primary sulphides by low temperature phases is restricted to the northern limb of the intrusion and results in heterogeneous distributions and elevated concentrations of As, Pd, Ag and Bi along fractures. Zonation of As, Mo, Ru, Rh, Re and Bi is observed in both pentlandite and chalcopyrite. Within the globular ores, petrographic observations suggest the pyrrhotite-chalcopyrite contact with which ‘contact’ pentlandite resides along, may not be indicative of the initial boundary between monosulphide solid solution (MSS) and the residual sulphide liquid. This has implications for the interpretation of trace element zonation patterns, which in the case of this study are not considered to be indicative of formation by peritectic reaction. This is further supported by the spatial distribution of multivariate clusters which show features in the granular and contact pentlandite that are consistent with exsolution from MSS.Within the locally vapour saturated taxites of the southern limb, a new microfabric is documented within the globular ores, revealing a close spatial relationship between enhanced trace element concentrations and microstructures within undeformed magmatic sulphides. The microfabric, which is defined by V, Cr, As, Pb and Bi and less frequently by Mo, Rh, Pd and Re, is prevalent in unaltered coarse pyrrhotite and in contact, granular and fan textured pentlandite, and is developed in association with both silicate-capped and uncapped sulphide globules. Regardless of the exact mechanism by which the microfabric formed (e.g., fluid interaction, exsolution, gravitational compaction), this study highlights that regional deformation is not required to drive the preferential enrichment of select elements along discrete planes. Only as more high resolution element map data become available will it become apparent if the microfabric is a common feature of magmatic Ni-Cu-PGE deposits or a unique characteristic of the Crystal Lake Intrusion.

Time Constraints of Late Cenozoic Tectonic Deformation of the Atushi Anticline, Southwestern Tian Shan: Evidence From Cosmogenic Nuclide Burial Age

With the latest uplift episode of Tian Shan occurring since early Miocene, a series of thrust–fold belts were formed in front of Tian Shan. The Kashi foreland thrust–fold belt (KFTB) provided a unique case to understand the ongoing intracontinental deformation within the Pamir–Tian Shan convergence zone (PTCZ). Previous cosmogenic nuclide chronological studies on growth folds suggested that the young thrust–fold belt in front of Pamir formed during 6–1.07 Ma. However, the age constraints of late Cenozoic deformation in front of southwestern Tian Shan are still debated. In this study, we attempt to constrain the initial deformation time of the NEE-striking Atushi anticline (ATA) in the KFTB through the cosmogenic nuclide burial dating data of growth strata near the boundary between Pliocene–Pleistocene Atushi Formation and Xiyu Formation (Xiyu Conglomerate), which are exposed in the southern limb of ATA. Moreover, detailed geological interpretations of multiple remote sensing images and field investigations are also carried out to document the late Cenozoic structural deformation and geomorphologic features of ATA. The 26Al/10Be burial dating data of four fine-grained samples reveal that the syntectonic deposit of ATA initiated at 1.79 ± 0.16 Ma, and the deposit of Xiyu Conglomerate started since 1.67 ± 0.18 Ma. Thus, we suggest that the thrust–folding of ATA began at ca.1.79 Ma and is currently still active.

Secondary faulting plays a key role in regulating the Cenozoic crustal deformation in the northeastern Qinghai‐Tibet Plateau

AbstractIn this study, channel steepness and main divide migration analysis were conducted on the Qinghai Nanshan to confirm the activity and evolution of the range. The results showed that the broad and gently dipping northern limbs correspond to relatively low steepness values, while the narrow and steeply dipping southern limbs are characterized by higher steepness distribution. In addition, main divide of the range is currently stable, despite its tendency migrating northward. Based on previous numerical simulations and our geomorphological results, we suggested that the Qinghai Nanshan thrust Fault is tectonically active. The sustained thrust activities of the fault have uplifted the Qinghai Nanshan, driven southward migration of the main divide and caused obvious regional crustal shortening and thickening. Given the same landscape characteristics as the Qinghai Nanshan, the Gonghe Nanshan was found to have appreciable influence on regional crust deformation. Secondary active tectonics (e.g. the Qinghai Nanshan and Gonghe Nanshan) could subdivide rigid blocks into smaller ones and promote the slip transferring and strain regulation between boundary strike‐slip faults. In summary, we concluded that continuous crustal deformation within the northeastern Qinghai‐Tibet Plateau is implemented through strain assimilation by minor faults in minor blocks.

Detachment folding, growth mechanism and seismic potential in the Jammu Sub-Himalaya

The Surin Mastgarh anticline (SMA) marks the active deformation front in the northwest Sub-Himalaya near Jammu. The southern limb of the SMA is not truncated by an emergent thrust, unlike other frontal folds along the Himalayan front. We investigate the structural data, deformation pattern, and seismic potential of the SMA using field surveys and re-interpretation of seismic profile. Strath profiles along the Chenab and the Munavar Tawi river valleys indicate active growth of the SMA by layer parallel shortening, and limb rotation accompanied by flexural slip, suggesting an early phase of its development. Lateral migration of the southern limb suggesting limb lengthening and bending at the hinge are the dominant mechanisms of fold amplification with strain localization at the fold core above the floor thrust tip. Bending moment faulting at the hinge led to the formation of crestal grabens or lakes in the southeastern section of the SMA. Our results suggest the existence of a weak, less viscous layer beneath a brittle sedimentary detachment. The SMA initiated as a detachment fold and sequentially deformed by passive roof thrusting. Therefore, the seismotectonic model of the Jammu Sub-Himalaya is different from that of the central and eastern Himalaya.

Hybrid Mapping of the Black Hole Shadow in M87

Abstract We present a reanalysis of the Event Horizon Telescope 228 GHz observations of M87. We apply traditional hybrid mapping techniques to the publicly available network-calibrated data. We explore the impact on the final image of different starting models, including the following: a point source, a disk, an annulus, a Gaussian, and an asymmetric double Gaussian. The images converge to an extended source with a size ∼44 μas. Starting with the annulus and disk models leads to images with the lowest noise, smallest off-source artifacts, and better closure residuals. The source appears as a ring, or edge-brightened disk, with higher surface brightness in the southern half, consistent with previous results. Starting with the other models leads to a surface brightness distribution with a similar size, and an internal depression, but not as clearly ringlike. A consideration of visibility amplitudes versus UV-distance argues for a roughly circularly symmetric structure of ∼50 μas scale, with a sharp edge, based on a prominent minimum in the UV-distribution, and the amplitude of the secondary peak in the UV-plot is more consistent with an annular model than a flat disk model. With further processing, we find a possible modest extension from the ring toward the southwest, in a direction consistent with the southern limb of the jet seen on 3mm VLBI images on a factor of few larger scales. However, this extension appears along the direction of one of the principle sidelobes of the synthesized beam, and hence requires testing with better UV-coverage.

Biostratigraphy and Facies Analysis of Upper Valanginian-Upper Hauterivian (Sarmord Formation) in Maten Anticline, Northern Iraq

Biostratigraphical and sedimentological study of the Sarmord Formation (Upper Valanginian - Upper Hauterivian) at the southern limb of Maten anticline is conducted within a well-exposed section. The formation is composed of marl, marly limestone, limestone, and dolostone, which yielded moderately diversified benthonic foraminiferal fauna, green algae, echinoderms, gastropods and some bioclast. The stratigraphic distribution of the benthonic species permits the recognition of two well-defined biozones. These are Everticyclammina kelleri Assemblage Zone, which represents the Late Valanginian age and Pseudocyclammina lituus Assemblage Zone, indicating Hauterivian age. These larger benthonic foraminiferal biozones are correlated with other zonal schemes inside and outside of Iraq, which indicates that the age of the Sarmord Formation in Maten anticline extends from Late Valanginian to Late Hauterivian age. The Sarmord Formation in the studied section is composed of limestone, dolomite, marl and conglomerate lithofacies types. Limestone lithofacies is represented by lime wackestone microfacies. According to the characteristic features of these facies, the depositional environments extend from tidal flat to shallow open marine environments.

Evaluation of the Rocks of The Pila Spi Formation of Duhok Anticline For Building Stones – Kurdistan Region Of Iraq

The rocks of the Pila Spi Formation at the southern limb of the Duhok anticline have been evaluated for use as building stones. The geology of the area and examined rocks are described. Nine samples were collected and tested for physico-mechanical properties (total porosity, water absorption, saturation coefficient, apparent specific gravity, bulk density and uniaxial compressive strength). There was a remarkable variation between the samples in these properties, which showed very high significant relationships with each other. Samples were classified as frost-resistant. According to the Iraqi and American Standards, four samples were categorized as (low density/acceptable), three samples as (moderate density/recommended) and two samples as (high density/highly recommended). According to some classifications, the samples were (moderately strong) except for two of them were (strong), while all of them were (moderately strong) and (high strength rocks) in other classifications. The examined rocks are suitable for interior and exterior wall cladding and exterior fencing, as well as for decoration. Four of them are not suitable for building sections that require high load bearing or in places where they come into contact with water or soil, such as foundations, while only two samples are suitable. The quality and quantity of the rocks and the quarrying conditions encourage their exploitation for building stones, with the necessity of proper planning of the proposed quarry and special treatment during quarrying.

Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean

The origin and tectonic implication of Early–Middle Devonian magmatism in the northern margin of YB (Yili Block) remain enigmatic and are important for understanding Late Paleozoic evolution of the Junggar Ocean and southern Kazakhstan Orocline. Here, we present the systematic study of whole-rock geochemical and Sr–Nd isotope features as well as U–Pb–Hf isotope characteristics of zircon crystals for newly identified Early Devonian volcanic rocks from the northern margin of YB. The volcanic rocks are composed of rhyolite, rhyolite porphyry, and rhyolitic tuff. Zircon U-Pb age dating indicates they were formed at ca. 407~418 Ma. They have high SiO2 (70.16–77.52 wt.%) and alkali (5.10–9.56 wt.%) contents, and high Zr + Nb + Ce + Y content (~456 ppm), indicative of A-type magma. Their relative depletion of Nb, Ta, and Ti, and enrichment of LILEs show arc affinity. Their low initial 87Sr/86Sr ratios (0.699708–0.709822) and negative εNd(t) values (−1.8 to −4.0) indicate a mainly continental magma source and their positive εHf(t)values (+6.13 to +14.81) are possibly due to the garnet effect. All these above reveal that volcanic rocks were generated by re-melting of lower crust under a high temperature condition, which was induced by long-lived heat accumulation with no or minimal basalt flux. Combined with active continental margin inference evidenced by contemporaneous sedimentary rocks, we attribute the generation of the volcanic rocks to a continental arc setting related to the southward subduction of Junggar oceanic crust. Thus, we infer the Early–Middle Devonian arc-related magmatic rocks in the northern margin of YB are eastward counterparts of the southern limb of the Devonian Volcanic Belt, which resulted from a relatively steady-state southward subduction.

Determination of Rock Slope Stability Using Stereographic Projection between Sulav and Amadiyah Resorts

Geological discontinuities play a significant role in the assessment of rock slope stability. Rock slope stability has been studied on the main road between Sulav and Amadiya resorts in Duhok governorate on the southern limb of Mateen anticline, to determine the expected rock slides on this road. Five (5) stations were chosen to study these rock slides that may occur on these steep slopes. All these stations within Pila Spi Formation that consists of hard dolomitic limestone and covering the areas from Sulav resort towards Amadiya district with a length of up to 2.5 Kms. The Stereographic analysis was used to study and classify the stability of these slopes. The analysis showed in all stations the possibility of plane sliding to happen on the bedding plane, and the wedge sliding between the bedding plane and planes of all joint sets, as well as the occurrence of rockfall on some stations.

Imprint of seasonality changes on fluvio-glacial dynamics across Heinrich Stadial 1 (NE Atlantic Ocean)

The northern Bay of Biscay has previously proven its great potential for recording the ‘Fleuve Manche’ paleoriver (i.e., the largest Pleistocene river in Europe) fluvio-glacial activity. In this study, new dinoflagellate cyst (dinocyst) analyses have been carried out at sub-centennial resolution in core MD13–3438 to reconstruct the deglacial history of the ‘Fleuve Manche’ paleoriver runoff coupled with European Ice Sheets (EIS) fluctuations across Heinrich Stadial 1 (HS1: 18.2–14.6 ka BP), a key extreme climatic event of the last glacial period. Prior to Heinrich Event (HE) 1 (16.7–14.6 ka BP), the onset of HS1 (18.2–16.7 ka BP) appears here marked by enhanced ‘Fleuve Manche’ paleoriver runoff, materialized by laminated deposits. Our work suggests a novel sub-centennial scale subdivision of the early HS1 (laminated) interval into 5 sub-phases when episodes of substantial fluvio-glacial delivery concomitant with warm summers alternate with episodes of moderate runoff associated with extended cold winters. We argue that multidecadal seasonal changes played a key role in the hydrological regime of western Europe during this HS1 interval, with the retreat of the southern limb of the EIS, and associated influx of meltwater and fluvio-glacial delivery, which were strongly influenced by those multidecadal changes in seasonality. Interestingly, our paleoclimatic record not only evidences the crucial role of seasonality in controlling climate and hydrological variations during HS1 but also shows a remarkable echo with reconstructions from the western Mediterranean Basin, highlighting common climate forcings at regional scale during the last deglaciation.

Geomorphological and Statistical Assessment of Tilt-Block Tectonics in the Garhwal Synform: Implications for the Active Tectonics, Garhwal Lesser Himalaya, India

Active tectonics is manifested in geomorphological features such as drainage basins and drainage patterns. Geomorphic parameters asymmetry factor (AF) and transverse topography symmetry factor (T) is calculated for 94 third order basins of the Garhwal synform to decipher the tilt-block tectonics based on remote sensing and geographical information system (GIS) techniques. The quantitative analysis of the AF suggests that all the 94 basins are asymmetric and gentle to steeply tilted, indicating active tectonics and early and late stage of development, respectively. The mean vector magnitude (θv) of T suggests the migration of the basin stream towards the south in most basins (60%), suggesting a unidirectional tilting of the tectonic block. The χ2 test for statistical significance indicates that the θv is significant for southern and northern limb basins. The χ2 test affirms that the third order basin position on either side of the main channel of the river basin influences the tilt direction. The regional tectonics suggests migration of the Lansdowne klippe towards the south, as the majority of third order basins show southward tilt. The study provides a quick appraisal of tilting in the tectonic blocks of active margins, such as in the Himalayas.

Late Oligocene\u2014Early Miocene shortening in the Thrace Basin, northern Aegean

Late Cenozoic was a period of large-scale extension in the Aegean. The extension is mainly recorded in the metamorphic core complexes with little data from the sedimentary sequences. The exception is the Thrace Basin in the northern Aegean, which has a continuous record of Middle Eocene to Oligocene marine sedimentation. In the Thrace Basin, the Late Oligocene–Early Miocene was characterized by north-northwest (N25°W) shortening leading to the termination of sedimentation and formation of large-scale folds. We studied the stratigraphy and structure of one of these folds, the Korudağ anticline. The Korudağ anticline has formed in the uppermost Eocene–Lower Oligocene siliciclastic turbidites with Early Oligocene (31.6 Ma zircon U–Pb age) acidic tuff beds. The turbidites are underlain by a thin sequence of Upper Eocene pelagic limestone. The Korudağ anticline is an east-northeast (N65°E) trending fault-propagation fold, 9 km wide and 22 km long and with a subhorizontal fold axis. It is asymmetric with shallowly-dipping northern and steeply-dipping southern limbs. Its geometry indicates about 1 km of shortening in a N25°W direction. The folded strata are unconformably overlain by Middle Miocene continental sandstones, which constrain the age of folding. The Korudağ anticline and other large folds in the Thrace Basin predate the inception of the North Anatolian Fault (NAF) by at least 12 myr. The Late Oligocene–Early Miocene (28–17 Ma) shortening in the Thrace Basin and elsewhere in the Balkans forms an interlude between two extensional periods, and is probably linked to changes in the subduction dynamics along the Hellenic trench.

The northern Appalachian terrane wreck model

Ordovician and Siluro-Lower Devonian magmatic rocks in the northern Appalachians south of the Iapetus suture are currently interpreted as distinct belts composed of multiple, small, peri-Gondwanan terranes that amalgamated during the sequential closures of Iapetus (latest Ordovician), the Tetagouche backarc basin (early Silurian), the Acadian seaway (Siluro-Devonian), and the Rheic Ocean (Devono-Carbonferous) (multiple terrane model). Here, the Siluro-Lower Devonian magmatic belts are shown to have slab failure affinities and together with the Ordovician arcs form paired belts parallel to the Iapetus suture, which suggests that they were emplaced along the common, peri-Avalonian margin during pre- and post-collisional processes. The Iapetan suture and the paired belts are inferred to repeat in Atlantic Canada due to dextral, strike-slip processes of mid-Late Devonian or younger age (terrane wreck model). In Newfoundland, the repetition is inferred to be the result of oblique, dextral offset of ca. 250 km. In the Quebec Embayment, the Iapetan paired magmatic belts are repeated twice in the limbs of a Z-shaped orocline related to oblique, dextral offsets of ca. 1200 km of the southern limb. Limited Siluro-Devonian paleomagnetic data indicate no paleolatitudinal differences across the Iapetus suture, however ca. 100° post-mid Silurian clockwise rotation is indicated for the middle fold limb; these data favour the terrane wreck model. The terrane wreck model results in a simple tectonic scenario of southerly subduction of Iapetus beneath a single ribbon continent (Avalonia sensu lato) that was subsequently deformed.

Pluri-Decadal Variability of Fluvio-Glacial Dynamics Across Heinrich Stadial 1: Dinocyst Evidence for Seasonality Changes in Western Europe

The northern Bay of Biscay has proven, in previous studies, its great potential for recording fluvio-glacial activity thanks to its proximity to the mouth of the ‘Fleuve Manche’ paleoriver, the largest Pleistocene river in Europe. In the present work, new dinoflagellate cyst (dinocyst) analyses have been carried out at pluri-decadal resolution in core MD13-3438. Our principle objective is to reconstruct the deglacial history of the ‘Fleuve Manche’ paleoriver runoff coupled with European glacial fluctuations across Heinrich Stadial 1 (HS1: 18.2-14.6 ka BP), a key extreme climatic event of the last glacial period. We identify warm conditions preceding HS1, at the end of the Last Glacial Maximum, highlighted by a significant penetration of the warm and salty North Atlantic Drift (NAD) at the study site. The onset of HS1 is marked by enhanced ‘Fleuve Manche’ paleoriver runoff leading to the formation of laminated deposits, here referred to as the ‘HS1-a laminated interval’. We also suggest a novel pluri-decadal scale subdivision of HS1 in 7 sub-phases including 5 sub-phases within the laminated interval (HS1-a1 to HS1-a5: 18.2–16.7 ka BP) and 2 sub-phases during the Heinrich Event 1 (HE1: HS1-b: 16.7–15.6 ka BP including the ‘conventional’ HE1 layer at ~16 ka and HS1-c: 15.6-14.6 ka BP). Within HS1-a, substantial terrigenous inputs are coeval with high marine primary productivity and large sea surface salinity drops, with reconstructed values as low as 29 psu at the study site. This results from substantial fluvio-glacial delivery of the ‘Fleuve Manche’ paleoriver in response to the seasonal influx of meltwater associated with the retreat of the southern limb of the European Ice Sheets. Additionally, in this interval, pluri-decadal variability is here detected. Two major events (HS1-a2: 17.8–17.6 ka BP and HS1-a4: 17.4–17 ka BP) of huge fluvial inputs (i.e., substantial erosional processes in the ‘Fleuve Manche’ basin and strong stratification of the water column) are revealed, and occur concomitantly with warm summers. In the rest of HS1-a (HS1-a1: 18.2–17.8 ka BP, HS1-a3: 17.6–17.4 ka BP and HS1-a5: 17–16.7 ka BP), fluvio-glacial discharges via the ‘Fleuve Manche’ paleoriver, although significant, were comparatively moderate induced by decreased seasonality dominated by extended cold winters that could have limited the EIS melting. We argue for the main role of seasonality (i.e., temperature contrast between summer and winter) within HS1-a in controlling fluvio-glacial dynamics. Subsequent intervals HS1-b and HS1-c (first and second phase of HE1, respectively), show a significant decrease of fluvial inputs as well as extended sea-ice cover occurrences and extremely low sea surface temperatures (-1.8°C), especially during HS1-b (associated to Laurentide-sourced Ice Rafted Debris). At the end of HS1-c, the NAD influence in the study area marks the onset of the transition to the warm Bolling/Allerod interval.Interestingly, our paleoclimatic record (i) confirms the crucial role of seasonality in controlling climate variations during the HS1 interval and (ii) shows a remarkable echo with reconstructions from the western Mediterranean Basin, highlighting common regional forcings acting on multi-scale climate variability during the last deglaciation.

Active Tectonics and Paleoseismicity of the Eastern Issyk-Kul Basin (Kyrgyzstan, Tien Shan)

Abstract—The Malyi Orgochor, Orgochor, Birbash, Sukhoi Ridge, Ichketosma, and Tosma uplifts in the eastern Issyk-Kul basin are fault-related anticlinal folds composed of Neogene and Quaternary sediments involved in tectonic movements. The folds have asymmetric transversal profiles, with low-angle southern limbs and steep northern limbs cut by segments of the South Issyk-Kul and Karkara reverse faults reactivated in the late Quaternary. The location and geometry of the two faults, which both show reverse and left-lateral strike slip components, correspond to neotectonic propagation of deformation from the Terskey-Ala-Too Range over almost the whole eastern Issyk-Kul basin. Judging by primary and secondary coseismic surface deformation in the area, the South Issyk-Kul and Karkara faults repeatedly generated large earthquakes (M ≥ 7, I ≥ 9) in the Late Pleistocene and Holocene. According to trenching results, the historical earthquakes that occurred in the first and 10–11th centuries accommodated motions on the South Issyk-Kul fault. The new seismotectonic and paleoseismicity data from the eastern Issyk-Kul basin provide updates to its seismic potential.

Determining the Tectonic Origin of the Gara and Mateen Anticlines Using Geomorphological and Structural Forms, Iraqi Kurdistan Region

Gara and Mateen are 2 major anticlines in the northern part of the Iraqi Kurdistan Region, located in the vicinity of the town Amadiyah. Both anticlines are oriented in an almost east–west (E–W) trend with a steep southern limb. The length and width of the Gara and Mateen anticlines are 87 km and 63 km, and 11 km and 9.5 km, respectively. The 2 anticlines are separated by a wide and shallow syncline filled by the Tertiary rocks of the Pliocene–Pleistocene age. The oldest exposed rocks in the Gara and Mateen anticlines are from the Triassic age. The carapace of both anticlines is built up by the Bekhme and Qamchuqa formations. The geomorphological and structural features were studied through satellite images and geological maps. Based on these studies, it was found that both anticlines show clear geomorphological and structural features that indicate their lateral growth. Among those features are water and wind gaps, different shapes of valleys that indicate lateral growth, abandoned alluvial fans, whale-back shapes, en-echelon plunges, and multiple dome anticlines. Furthermore, the rate of upward movements was calculated using neotectonic data. In addition, the rate of river and stream incisions was calculated on the basis of the height of the river terrace levels.

Study of the Quaternary Deposits at the East and West Shoulders of Mosul Dam Using Azimuthal 2D Resistivity Imaging

The field survey included three geoelectric traverses on the eastern side of the Tigris River parallel and perpendicular on the axis of the Tairah anticline consisting of seven sites of ( Azimuthal Resistivity Tomography; ART) located above the Quaternary depositions in the southern flank. Two traverses were also conducted in the western side of the river parallel and perpendicular on the east Butmah anticline consisting of four sites located above the recent sediments in the southern flank of it. The sites are chosen taking into account the consideration of the geological, tectonic and topographic data of previous studies and current field reconnaissance trips. A sympathetic analysis of the resistivity tomography is performed in nine azimuths of the above mentioned locations using fifteen repetitive processing attempts and the mean root squares ranged between 5.8% -11.7%. The eastern side of the study area with different directions indicates electrical horizons, the first reflects a variable resistivity which represents accumulations of top soil, the second band of high resistivity which reflects the river terraces constitutes, while the third horizon represents the clear extension of the mud and limestone deposits of Fatha Formation with a vertical conductive zones in the rock layers at some traverses. As well as the ART on the western side of the study region identified three electric horizons: the first with high resistivity reflecting the surface soil layer, and the second domain of low resistivity representing the sediments of the valley slopes and concentrating on the southern limb of Butmah anticline. The third of heterogeneous resistivity values reflects Fatha Formation deposits covering its exposures at the core of the two anticlines and locating beneath the research traverses. Using the technology of 2D resistivity imaging reveals that the nine orientations around a central point in eleven locations above recent sediments are represented by river terraces and alluvial deposits on the shoulders of the Mosul Dam. The current study concludes the ability to capture fractures, which is of great importance due to their effect on the displacements of the dam's body and Fatha sediments surrounding it.

Fan morphology evidence on Late Quaternary deformation in the southern front of the Central and Eastern Alborz Mountains in the Eyvanekey, Garmsar, Semnan areas, Northern Iran

Although numerous studies have been done on the Alborz Mountains, few have examined Quaternary events based on alluvial fans which are located in front of the southern limb of the Central and Eastern Alborz Mountains. This study analyzed the morphometric indexes for 131 alluvial fans (three generations) in the Eyvanekey, Garmsar, and Semnan areas (As, WLF, Bull, Fa, Fs, Fg, Fc, R) as well as for basins (Da, AF, T, Bs), mountain fronts (Fmf, Smf, Vf, Fd), and rivers (Sl). The morphometry results show that a young deformation in this area has caused on uplift in the crust along structures in the Alborz. The Garmsar area is more active than the Semnan area in which both are more active than the Eyvanekey area. All of the alluvial fan evolution in this area relate to the Quaternary events. The study on the information obtained from the exploitation wells and geoelectric profiles of the region shows that the Alborz uplift in the north is associated with the erosion and deposition of the new deposits in the form of alluvial fans. The bedrock behavior at the base of the fans has a direct effect on the formation of the second- and third-generation fans. The effect of the continual compressional tectonics in the Late Quaternary is associated with the uplifting evaporite masses, the uplifting hanging walls of the reverse faults, and the growth of the folded structures.

Petrographic characteristics of deep marine turbidite sandstones of the Upper Cretaceous Tanjero Formation, Northwestern Sulaimaniyah, Iraq: implications for provenance and tectonic setting

This study was carried out to determine the sedimentary provenance of Upper Cretaceous turbidites of Tanjero Formation. The sandstone portion of the unit has been examined based on field and laboratory studies. Seven sections were measured and described in detail on the perfectly cropped out part of the unit at the southern limb of the Sulaimaniyah Syncline. The thickness of the measured sections varies from 120 m to 192 m. The measured sections start from the top of the underlying Shiranish Formation to the syncline axis in the Tanjero Formation. For petrographic analysis sixty- nine representative rock samples were collected. Modal analysis and ternary diagrams point out that, the sandstones are calclithite (litharenite), very fine to medium grained in size consisting of chert, siltstone, mudstone, radiolarian chert and radiolarian mudstone fragments, angular to subangular in shape, very poorly to moderately sorted, transported over short distances and represent submature stage. Grain contact types and high contact index (4.7) indicate moderate to tightly packing, moderate compaction. Transported broken neritic fossil shells, moderately rounded glauconite grains, and undefinable fossils in the altered carbonate rock fragments indicate that the tectonic provenance, lithic recycle category, composed of not only the clastics as interpreted in previous studies derived from Lower Cretaceous Qulqula (radiolarian) Formation which represents deep marine, but also it revealed that a sedimentary formation must also exist in the source area, which is the Lower Cretaceous Balambo Formation.

Fluid Dynamics in a Thrust Fault Inferred from Petrology and Geochemistry of Calcite Veins: An Example from the Southern Pyrenees

Petrographic and geochemical analyses (δ18O, δ13C, 87Sr/86Sr, clumped isotopes, and elemental composition) coupled with field structural data of synkinematic calcite veins, fault rocks, and host rocks are used to reconstruct the episodic evolution of an outstanding exposed thrust zone in the Southern Pyrenees and to evaluate the fault behavior as a conduit or barrier to fluid migration. The selected thrust displaces the steeply dipping southern limb of the Sant Corneli-Bóixols anticline, juxtaposing a Cenomanian-Turonian carbonate unit against a Coniacian carbonate sequence. Successive deformation events are recorded by distinct fracture systems and related calcite veins, highlighting (i) an episodic evolution of the thrust zone, resulting from an upward migration of the fault tip (process zone development) before growth of the fault (thrust slip plane propagation), and (ii) compartmentalization of the thrust fault zone, leading to different structural and fluid flow histories in the footwall and hanging wall. Fractures within the footwall comprise three systematically oriented fracture sets (F1, F2, and F3), each sealed by a separate generation calcite cement, and a randomly oriented fracture system (mosaic to chaotic breccia), cemented by the same cements as fracture sets F1 and F2. The formation of fractures F1 and F2 and the mosaic to chaotic breccia is consistent with dilatant fracturing within the process zone (around the fault tip) during initial fault growth, whereas the formation of the latest fracture system points to hybrid shear-dilational failure during propagation of the fault. The continuous formation of different fracture systems and related calcite cementation phases evidences that the structural permeability in the footwall was transient and that the fluid pathways and regime evolved due to successive events of fracture opening and calcite cementation. Clumped isotopes evidence a progressive increase in precipitation temperatures from around 50°C to 117°C approximately, interpreted as burial increase linked to thrust sheet emplacement. During this period, the source of fluid changed from meteoric fluids to evolved meteoric fluids due to the water-rock interaction at increasing depths and temperatures. Contrary to the footwall, within the hanging wall, only randomly oriented fractures are recognized and the resulting crackle proto-breccia is sealed by a later and different calcite cement, which is also observed in the main fault plane and in the fault core. This cement precipitated from formation fluids, at around 95°C, that circulated along the fault core and in the hanging wall block, again supporting the interpretation of compartmentalization of the thrust structure. The integration of these data reveals that the studied thrust fault acted as a transverse barrier, dividing the thrust zone into two separate fluid compartments, and a longitudinal drain for migration of fluids. This study also highlights the similarity in deformation processes and mechanisms linked to the evolution of fault zones in compressional and extensional regimes involving carbonate rocks.