Igneous Mass Research Articles

GEOPHYSICAL EXPLORATIONS BY RESISTIVITY AND INDUCED POLARIZATION METHODS FOR THE COPPER DEPOSIT, SOUTH KHORASAN, IRAN

Link for citation: Adel Shirazy, Ardeshir Hezarkhani, Aref Shirazi, Timkin T.V., Voroshilov V.G. Geophysical explorations by resistivity and induced polarization methods for the copper deposit, South Khorasan, Iran. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2022, vol. 333, no. 3, рр. 99-110. In Rus
 The relevance. These are the first geophysics studies in the Mesgaran exploration area. Based on geological studies in the mineral zone, copper mineralization was proven. The mineralization type in this area was identified as Cyprus-type massive sulfide. The complexity of the geological structure determines the need to use geophysical research and forecasting methods for planning mining and drilling operations. The main aim of this study is the application of geophysical methods in the search for mineral deposits and modeling of the geological environment. Object: Mesgaran exploration area, South Khorasan province, Iran. Methods. In order to obtain more subsurface information, geophysical methods IP and Rs were used. Five profiles were designed and implemented for geoelectric surveys. Overall, five profiles (P1 to P5) were read as dipole-dipole arrays with 784 points. The profiles were taken east-west and north-south along parallel to the mineralization zones. The dipole-dipole array is designed with the parameters AB=MN=20 m, jump=20 m and up to 6 jumps for MN. Results. In general, four types of anomalies were identified in these investigations. Which to some extent revealed the association of anomalies with the types of rocks and mineralization of the study area: 1) anomalies with low electrical resistivity, as well as low polarity, often correspond to quaternary alluvial deposits; 2) abnormalities with high electrical resistance, and low polarity, which are consistent with limestone’s and are often superficial; 3) anomalies with high polarity and high resistance, which in the south of the profiles form altitude and correspond to the agglomerates; 4) anomalies with high polarity and higher relative resistance are associated with igneous masses, which are often composed of andesitic-basaltic rocks. Based on the position of the identified anomalies in the 5 profiles, the optimal location of the drills was determined.

Geochemistry and genesis of igneous rocks and skarn of Shahrak iron ore (Northeast of Kurdistan)

Shahrak iron deposit is located at the north of Sheikh-Besharat village, northwest of the city Hassan-Abad Yasukand, Kurdistan province. The study area includes igneous rocks, skarn zone, metamorphic zone (marble), and iron ore. Igneous rocks exposed in the district include calc-alkaline volcanic rocks with the dominant composition of rhyolite, andesite, dacite, trachyandesite, volcanoclastic (tuff) and intrusive rocks of diorite and granodiorite type, and carbonate rocks of Qom Formation (Miocene). Based on field studies, petrography of volcanic rocks and the skarn zone and Fe ore mineralography in the area, it can be said that iron mineralization and skarn formation occur adjacent to the igneous masses. The skarn index minerals are evidence of this event. The spider diagram patterns of rare earth elements of the Shahrak deposit samples normalized to the chondrite indicate more enrichment in light rare earth elements (LREE) than heavy rare earth elements (HREE). Positive Eu and negative Ce anomalies are characteristic of hydrothermal iron ore deposits. The different pattern of trace elements in the igneous rocks and the ore indicates their various geneses. The less important role of low salinity non-magmatic fluids in ore formation is concluded by chemical analysis results.

9.尾鈴山酸性岩体の構造とその噴出様式 : 日本火山学会1976年度春季大会

9.尾鈴山酸性岩体の構造とその噴出様式 : 日本火山学会1976年度春季大会

A correlation between the Large Igneous Provinces and mass extinctions: constraint on the end-Guadalupian mass extinction and the Emeishan LIP in South China, eastern Tethys

ABSTRACTWell-documented outcrops around the Emeishan Large Igneous Province (ELIP) in South China, eastern Tethys, encompassing the end-Guadalupian mass extinction have been investigated. Correlatable sections recording the event exhibit very similar lithological characters, positive-then-negative C isotope excursions and massive biotic demise. Detailed analyses of the fossil record and carbon isotopic variations were carried out on the Guadalupian–Wuchiapingian Boundary sections over the inner, middle, outer zones of the ELIP and its margin. Due to a pronounced decrease in marine habitat area and the environmental and ecological change over this part of the Tethys, the biota crisis records show the loss of numerous tropical invertebrate taxa, and exhibit fewer genera and smaller testing sizes and low productivity. The biota crisis was a sustainable and gradual reduction in diversity over the Capitanian. The associated carbon isotopic data reveal unusually high δ13C(carb) values before the late Capitanian, representing higher primary productivity (or buried rate) and more 13C-enriched CO2 released by hydrothermal carbonate breakdown from the upper crust into the sediments at that time. Subsequently, an accelerated negative excursion across the boundary and the gradual excursion with low carbon isotope amplitude favours an increased influx of light 12C sourced by the volcanism around the eastern Tethys. The very similar time–space relation between the biota crisis and the Emeishan volcanism confirms that volcanic eruptions may have triggered the biota crisis event in South China. Intensive volcanism could result in detrimental environmental and ecological stresses, habitat loss, organic material splitting, or the emission of light carbon and thermal fluid (or aerosol), implying that the losses of the shallow-marine invertebrates either occurred geologically instantaneously or in a series of closely spaced crises coinciding with the initial phase of ELIP formation. These findings in South China may reveal the causal relation between mass extinctions and LIPs in a global context.

Tectomagmatic Origin of the Zahedan Batholiths – South East Iran (Reling on Intergrated Outcrop Study of the Petrology of High Mass in Loochan, Southwest Zahedan)

Zahedan batholiths, the largest intrusive igneous mass in Sistan Suture zone, in Southeast of Iran during the Eocene - Oligocene is formed in this zone. The mass of igneous outcrops in a narrow mass with scattered outcrops Larger populations with continuous advice, The Afghan Block of East and West Blocks of Lout outcrop at the surface, Granitoid batholiths magma intrusion in the petrographical Zahedan region specific and that the mass of Tectomagmatic origin of calc-alkaline and per aluminous igneous intrusion that is Melting of continental sedimentary rocks in the shallow crust Lateral movement of the compression zone includes the land area is under construction.

Extraction of gadolinium from El-Garra El-Hamra rare-earth cake, South Western Desert, Egypt

The study area of El-Garra El-Hamra is one of the igneous masses located in the southern part of the Western Desert of Egypt. This work has been carried out to investigate the process of gadolinium separation from REEs cake obtained from El-Garra El-Hamra ore concentrate. It is considered as a new approach in the Nuclear Materials Authority of Egypt. Firstly; the optimum leaching conditions achieved are 200 gm/L H2SO4, 1/2 solid/liquid ratio, 4 h agitation time,−125 mesh size and at 90 °C temperature. Then by solvent extraction method using 1 mol/L D2EHPA middle REEs were extracted. The organic extractant was stripped by using 2 mol/L HCl and Gd pregnant solution was obtained. Then, the relevant optimum factors were 0.3 mol/L D2EHPA diluted by kerosene, 10 min contact time, and 4/1 organic/aqueous ratio giving 87 % Gd extraction. Then, the scrubbing of the loaded extractant was by 1 mol/L HCL followed by Gd stripping using 5 M HCl, contact time of 30 min and 1/3 organic/aqueous ratio. The strip solution was subjected to evaporation and little amount was dried to obtain GdCl3 powder having a purity of about 81 % associated with YCl3 4 %.

Comparison of ASTER thermal data sets in lithological mapping at a volcano-sedimentary basin: a case study from southeastern Iran

The thermal bands of ASTER level 1B (L1B) and ASTER 05 (AST_05) data sets were used to map lithological units of an area situated in the southeastern Iranian volcano-sedimentary complex, Kerman Province. The dominant lithological units exposed at the area include felsic and mafic igneous rocks and carbonate masses. The thermal bands of L1B were atmospherically corrected and converted into emissivity using the Reference Channel, Emissivity Normalization, and Alpha Residual algorithms. The Spectral Angle Mapper (SAM) algorithm was implemented on the calibrated L1B and AST_05 data sets. The reference spectra were derived from the image using a spectral endmember selection procedure including minimum noise fraction (MNF), pixel purity index (PPI), and n-dimensional visualizer. Results were compared to the geological map of the study area to determine the accuracy of lithological mapping. The SAM algorithm showed reliable results for discriminating felsic, intermediate to mafic, carbonate, and quartz-sandstone units. AST_05, Reference Channel, and Emissivity Normalization showed approximately similar results with overall accuracy 83, 80.2 and 79.20, respectively. The Alpha Residual data set is less effective in identification of lithological units, as evidenced by a low overall classification accuracy of 50.5. It is concluded that AST_05, Reference Channel, and Emissivity Normalization data sets are suitable for lithological mapping by ASTER data.

Vein-type Deposits around the Intrusive Igneous Masses

Vein-type Deposits around the Intrusive Igneous Masses

A Rapid Graphical Solution for Determining the Presence of Remnant Magnetization in the Basement Rocks of Western Iraq

A Rapid Graphical Solution for Determining the Presence of Remnant Magnetization in the Basement Rocks of Western Iraq

Reply to comments on "Is stoping a volumetrically significant pluton emplacement process?"

The 188th meeting of the Geological Society of Washington “was devoted to a consideration of the ‘Methods of Igneous Intrusion.’ The discussion was opened by Mr. Whitman Cross, who directed it to the methods by which the large igneous masses, such as laccoliths, stocks and batholiths, have

The Effect of Adjacent Magnetic Sources on the Interpretation of Magnetic Anomalies

In interpreting magnetic profiles from the aeromagnetic map of Iraq, it is usually assumed that the observed anomalies are caused by homogeneous magnetic bodies forming the basement that is concealed beneath a thick cover of sediments. Many unknowns are faced in interpreting magnetic anomalies related to such deep sources. Among these: direction of magnetization in these sources, magnetic susceptibility and the contributions of the adjacent sources are the most important unknowns. Therefore, it is to be assumed that these anomalies are related to igneous bodies within the basement rocks and magnetized by induction only from the present earth’s magnetic field. In other word, the study is focused on one of the unknowns mentioned above, which is the effect of contribution of adjacent igneous body at different depths and sizes on the shape of main magnetic anomaly. Previous studies related to interpretation of aeromagnetic anomalies in Iraq, have assumed that these basement anomalies are not affected by adjacent igneous masses and as such not taken in consideration, (Al Mashhadani, 2000, Najar, 1999, Mohammed 1981, Mahmood, 1981, Aziz, 1981). In this paper ,the effects of such close magnetic sources will be considered . The suggested method is designed at estimating the amount of change in the -ve part of the anomaly occurring between two igneous sources, which in turn depends on how close the adjacent igneous sources to the main one.

THE AGE OF THE HAWASINA AND OTHER PROBLEMS OF OMAN MOUNTAIN GEOLOGY

It is now popular to interpret the geological evolution of the Oman Mountains within the framework of the plate‐tectonic paradigm. Current interpretations hold that the deep‐water Hawasina sediments, huge exotic limestone blocks and the overlying Semail serpentinite originated in a Tethyan Ocean to the north of the present‐day mountains in Permian to Senonian time. In the Late Cretaceous, continental collision telescoped these oceanic rocks and thrust them southward over the autochthonous carbonate platform where they are now exposed. The origin of turbidites, debris flows and exotic blocks in the Hawasina complex is interpreted to have been a north‐facing continental margin that bordered the Tethys Ocean. Howevel; Permian to Cenomanian limestones that are exposed all along the axis of the Oman Mountains show no sign of penecontemporaneous rifing and erosion. If the supposed shelf‐edge ever existed, it is now hidden from view.There are some serious questions that counter the popular model. The long duration of deep‐water deposition is predicated upon the assumption that cleanly‐reworked shallow‐water benthonic fauna in the Hawasina turbidites were derived penecontemporaneously from shelf sediments and are therefore age indicative. This is a subjective judgment that can be challenged, because clean, recycled fossils from older consolidated formations are common constituents of deep‐water turbidites worldwide. Also, the dissolution of contemporaneous pelagic microfauna below the Carbonate Compensation Depth is supported by present‐day analogues.Where faunal inversions occur in a bedded succession, the palaeontological assumptions force a structural interpretation of repetition by thrusting. Howevel; in the Oman Mountains, massive thrusts interpreted to have horizontal displacements of over 100 km from a supposed Tethyan ocean basin appear to lack the expected disruption in the field. For example, in Wadi Miaidin, supposedly Jurassic sandstone turbidites of the Guwayza Formation (part of the Hawasina) appear to rest on the autochthonous Coniacian Muti Formation without major structural disturbance. This lack of deformation across what is interpreted to be a major thrust plane casts serious doubt upon dating criteria and demands detailed structural analyses to resolve both structural and palaeontological assumptions.In the Al Ajal area on the north flank of the Oman Mountains, intra‐volcanic sediments resting below the Semail Ophiolite, which have previously been dated as Triassic, have yielded Senonian Globotruncana. This also raises doubts about dating based upon reworked fauna in deep‐water turbidites.The tectofacies of the Hawasina sediments with ubiquitous turbidites and debris flows are typical of thick and rapidly deposited sediments in a tectonically active environment. Howevel; the ffawasina succession is relatively thin for the assumed time span, and the Permian to Cenomanian autochthonous succession of monotonous platform carbonates is indicative of structural quiescence. On the other hand, regional extension and massive block faulting accompanied by rapid deep‐water sedimentation typijies the Senonian depositional environment, which would be in concert with Hawasina tectofacies.The huge Semail igneous mass is a layered rock sequence with dip slopes that conform to mid‐Tertiary deformation. rf the pre‐Tertiary structure is restored, the Semail serpentinite becomes virtually horizontal at the time of emplacement. This structural simplicity belies the contention that the Semail was first ejected from a deep mugma chamber and was then obducted onto continental crust. A sedimentary origin involving the erosion of rising hot simatic material and the monolithological deposition of disaggregated crystals by turbidity currents could explain the rhythmic bedding, pervasive serpentenisation and minimal deformation characteristic of the Semail.Although a plate tectonic interpretation for the occurrence of the Steinmann trinity in the Oman Mountains is now generally accepted, the field evidence for extensional tectonics and gravity gliding appears to outweigh the evidence for regional compression and thrusting. Further work may provide more support for previously held autochthonist interpretations.

The nature of the basement to the Cooper Basin region, South Australia

Analyses of aeromagnetic and gravity data in the Cooper Basin area of South Australia, reveals varied basement lithologies and structure. Most of the observed magnetic responses arise from sources beneath the Cooper Basin sequence. A prominent northeast-trending structural basement grain is evident. Emplacement of a large igneous mass into the upper crust is interpreted beneath the Patchawarra Trough. Interpreted faulting along the southeastern edge of the igneous body resulted in up to 3.5 km of block uplift, coincident with the Gidgealpa and Merrimelia Ridges. A broad and prominent gravity low in the Nappamerri Trough region is attributed to Late Carboniferous Big Lake Suite granodiorite masses, which have intruded Warburton Basin strata. Intense gravity lows within the broader gravity low are attributed to granodiorite cupolas, which became non-tectonic palaeo-topographic highs during Cooper Basin deposition. Another broad gravity low in the Tenappera Trough region is due to a belt of Early Devonian granitoids that have intruded Proterozoic basement. A number of small magnetic anomalies, in the south of the survey, are interpreted as sourced from skarns above and adjacent to the granitoid intrusions. The only magnetic units above Proterozoic basement in the region are the basalts in the Warburton Basin sequence, which coincide with small magnetic anomalies. Depth to magnetic source modelling correlates well with the known depths of the basalts.

Tectonics of the Venezuelan Borderland: An Interpretation of Magnetometer Surveys

Over 46,000 km of shipborne magnetic surveys and over 64,000 km of aeromagnetic surveys cover the offshore Venezuelan Borderland. The information from these surveys has been assembled into a total intensity map, together with its vertical gradient reduction, and interpreted with respect to the regional tectonics. The distribution and shape of the igneous intrusions and metamorphic rock masses can be clearly recognized as well as the major sedimentary troughs. Areas with similar frequencies and trend directions have been grouped into magnetic provinces in order to better delineate the different structural styles and picture the forces that acted on the basement rocks. The most prominent structures of the Borderland are the nappes and the major transcurrent faults, along which the provinces moved toward the southeast. In the Margarita Province the Margarita-Testigos and La Blanqilla nappes are the most conspicuous. The Delta Province, to the East, is characterized by the complex compression zones that have moved southeastward along the border of the craton. The La Vela region to the West comprises a complex of overriding magnetic provinces. In the exploration for traps with possible accumulations of hydrocarbons, the interpretation of the vertical gradient is the most important as it provides considerable detailmore » on structural patterns. The structures determined by vertical gradient maps coincide very well with those determined by seismic methods in those areas covered by seismic, and thusly, the magnetic maps serve as a reliable guide to structures in areas not yet covered by seismic surveys.« less

Geochemical characteristics of Jinwozi gold deposit, Xinjiang

The Jinwozi gold deposit consists of gold-bearing quartz veins in a biotite granodiorite of Hercynian age (zircon U-Pb age ≈ 335.7 Ma). Ore mineralogy is simple. In addition to native gold, there are only small amounts of sulfides, mainly pyrite and minor sphalerite, chalcopyrite and galena. δ34S values average 6.69‰, and δ18O 13.99‰ Abundant CO2 is contained in fluid inclusions from quartz. Homogenization temperatures of fluid inclusions are between 186 and 262 °C. REE distribution patterns indicate that the igneous mass may have been derived from a common initial material of calcareous-argillaceous sediments and alkali basalts as the country rocks. In other words, the Jinwozi granodiorite is of remelting origin from crustal material. Isotopic evidence of S, O and Pb shows that the ore-forming material is genetically related to magmatic hydrothermal activity.

Results of geoscience research in the Canadian Nuclear Fuel Waste Management Program: Introduction

Canada, along with other countries that are considering the permanent disposal of high-level radioactive wastes from nuclear power generation, is undertaking a program of research into deep geologi...

Early Cretaceous near‐trench plutonism in southern Alaska: Atonalite‐Trondhjemite Intrusive Complex injected during ductile thrusting along the Border Ranges Fault System

A group of leucotonalite to trondhjemite plutons in the western Chugach Mountains, Alaska, record a period of Early Cretaceous near‐trench plutonism along the paleo‐Alaskan/Aleutian subduction zone. The plutons were emplaced along the tectonic join between an older (Jurassic) arc massif and a younger (Cretaceous) melange terrane that was accreted by subduction beneath the crystalline massif. The plutonic rocks were injected during a major thrusting event that placed upper mantle(?) ultramafic masses atop the Cretaceous subduction assemblages. Deformation during this thrusting event apparently progressed from ductile to brittle conditions, and plutonic rocks were injected during both phases. Evidence for plutonism synchronous with ductile deformation includes boudinage or folding of leucotonalite dikes as well as a characteristic weak fabric within larger plutons. The latter is commonly associated with secondary mineral growth as well as deformation‐induced microstructures that suggest deformation under temperatures that decreased from lower amphibolite to subgreenschist facies conditions, conditions which are equivalent to the structural/metamorphic progression in adjacent schists. Paradoxically, however, the plutons locally crosscut low‐grade melange fabrics in the footwall as well as brittle fault networks within structurally higher parts of the crystalline hanging wall. The paradoxical field relationships are partially due to shuffling by early Tertiary(?) dextral strike‐slip faulting but are also indicative of plutonic emplacement over a period of time. The absolute age span of plutonism, however, need not have been long considering the syntectonic emplacement history. In particular, the deformation locally may have been melt‐dominated such that after initial injection of melts, the deformation was concentrated in the igneous masses. Lithologically, the plutons follow a low‐K series from diorite to muscovite‐garnet trondhjemite, a trend that is unusual in Phanerozoic terranes and is typically associated with Archean terranes. Moreover, the compositional trends are unlike the calc‐alkaline trend of near‐trench plutons studied by Hill et al. (1981). The tectonic mechanism for the near‐trench plutonic event is elusive, but shallow melting of amphibolite or metagreywacke along a young subduction zone provides the most reasonable explanations for the observations. However, an alternative model relating magmatic activity to a ridge‐trench encounter is also allowable. Nonetheless, in either model the genesis of the igneous rocks within a high‐temperature ductile thrust zone is atypical of modern subduction zones. Thus structural setting and lithologic association have many similarities to Archean systems, and the rocks may represent a young analog that ultimately may provide key petrogenetic constraints for the Archean system.

The south Celtic Sea/Bristol Channel Basin: origin, deformation and inversion history

The South Celtic Sea/Bristol Channel Basin is a relatively narrow and elongated sedimentary trough, located within the northern part of the Hercynian fold belt and filled with ?Permo-Triassic redbeds to Jurassic marine sediments. Its present configuration is the result of a three-fold sequence of tectonic phases initiated during the late Palaeozoic. The origin of the basin appears to be related to localised extensional reactivation of Hercynian thrust zones during the ?Permian and Early Triassic, followed by regional subsidence during the Late Triassic and Jurassic. Uplift of the basin margins, together with dextral strike-slip movements in an east-west sense and large-scale erosion during the Late Jurassic to Early Cretaceous, resulted in the present elongated configuration of the Lower Mesozoic basin. Regional subsidence from Aptian time onwards resulted in widespread deposition of a relatively thin section of Wealden elastics and Upper Cretaceous chalk, unconformably overlying folded pre-Cretaceous strata. Sedimentation was interrupted during the Early Tertiary by a series of tectonic events that included emplacement of the Lundy igneous mass during the Early Eocene and mild basin inversion during the Oligo-Miocene. Inversion was accompanied by dextral reactivation of the NW-SE oriented Sticklepath fault zone. The total amount of uplift, probably not exceeding 350 m, reflects the rather stable configuration of the underlying lithospheric crust as indicated by seismic reflection and refraction data.

Ore deposits of the western United States in relation to mass distribution in the crust and mantle

Colored, digital residual Bouguer gravity maps of the conterminous United States at different cutoff wavelengths reveal significant compositional heterogeneities in the lithosphere, providing a new tool for the studies of controls of mineralization. Examples are presented showing correlations between main endogenic ore deposits of the western United States and gravity anomalies in the residual Bouguer gravity maps at 250-, 625-, and 1,000-km wavelength cutoffs. Some of the clusters of ore deposits are in or adjacent to regions of gravity lows (for example, the majority of deposits of the Colorado mineral belt). Most of the high-amplitude gravity lows reflect low-density igneous masses emplaced along zones of tectonic weakness which guided the ascent of magmatic fluids and caused major geochemical changes in the lithosphere. Some clusters of ore deposits (for example, the group of Tertiary deposits of the Salt Lake City area, Utah, including Bingham, Tintic, Park City, and others) are along the flanks of major zones of gravity highs. In the Salt Lake City area, the major concentrations of metals occur near the eastern edge of a broad gravity high that correlates with crustal thinning. These relations (and others) between the location of major ore deposits and mass distribution in the crust and upper mantle may serve as general guidelines in mineral exploration on a regional scale.

Disruption of the ‘Younger Basic’ masses in the Huntly–Portsoy area, Grampian Region

Synopsis Continued investigations in the Huntly–Portsoy area have been assisted by the availibility of data from shallow drillholes, trenches and commercial geophysical surveys, and have shown that the ‘Younger Basic’ masses in this area have complex structures and relationships. Earlier maps of these masses have been modified and previously unrecognized bodies of deformed ‘Younger Basic’ rocks have been identified near Portsoy. It has been established that sheared and mylonitized ‘Younger Basic’ rocks occur widely and that the contact relations and internal structure of the igneous masses have been greatly disrupted by post-magmatic deformation. It is concluded that the ‘Younger Basic’ rocks in the Huntly–Portsoy area lie within an important mylonite zone which trends N–S and dips steeply, and is comparable to the mylonite zones which have affected the Belhelvie and Insch ‘Younger Basic’ masses.