New Insights into Interpretation of Aeromagnetic Data for Distribution of Igneous Rocks in Central Iran

2021 ◽  
Author(s):  
M. Mohammadzadeh Moghaddam ◽  
S. Mirzaei ◽  
M. Abedi
Keyword(s):  
Magnetic Susceptibility ◽  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Aeromagnetic Data ◽  
3D Inversion ◽  
Aeromagnetic Anomalies ◽  
Susceptibility Data ◽  
Lut Block ◽  
Wide Range ◽  
Intrusive Rocks

Abstract —New insights in the aeromagnetic data over the Central Iranian Microcontinent (CIM) have revealed interesting results for future studies and exploration. This work presents the interpretation of different magnetic analyses and the calculated 3D inversion model to provide important insights into the distribution of igneous rocks in the area that may be traced under significant cover. By analyzing several hundred magnetic susceptibility data points and aeromagnetic anomalies of known igneous rocks over the area, it was determined that mafic–ultramafic intrusive rocks generally have a high magnetic susceptibility and produce a strong magnetic response. Intermediate–felsic intrusive rocks have a low magnetic susceptibility and show a smooth gradient variation and commonly regular shape. Volcanic rocks show a wide range of magnetic susceptibility; therefore, the aeromagnetic anomalies are often random or show strong amplitude with high frequency signals and are rapidly eliminated when an upward continuation is applied. Based on the results of analysis of different magnetic maps and 3D inversion of data, and combining this information with known outcropped of igneous rocks, we revealed 1215 concealed intrusive rocks and 528 volcanic rocks in the area. We also renewed the boundaries of tens outcropped igneous rocks. The known and new mapped igneous rocks can be identified as 12 regions (or zones) for intrusive rocks and 4 regions for volcanic rocks. The results indicate that the mafic–ultramafic rocks are mainly located in the Sistan suture zone of eastern Iran along the Nehbandan fault zone. They also show that the many parts of the Lut block as the main structure of CIM have been under magmatic events, so that most of concealed igneous rocks are distributed in the middle and southern part of the Lut block. Volcanic rocks are widespread in the southeastern and northern parts of the area such as the Urumieh-Dokhtar Magmatic Arc, North Lut, and Bam region.

Density and magnetic susceptibility measurements in southeastern New Brunswick

1977 ◽  
Vol 14 (1) ◽  
pp. 128-132
Author(s):  
V. K. Gupta ◽  
K. B. S. Burke
Keyword(s):  
Magnetic Susceptibility ◽  
New Brunswick ◽  
Volcanic Rocks ◽  
Considerable Variability ◽  
Aeromagnetic Anomalies ◽  
Rock Types ◽  
Flow Units ◽  
Intrusive Rocks ◽  
Density Values

The results of over 200 density and 400 (at 37 sites) in-situ magnetic susceptibility measurements from southeastern New Brunswick are presented. Intrusive rocks were found to be homogeneous in density and to have values similar to those reported from adjacent areas of the Northern Appalachians. However, most of the Coldbrook volcanic rocks show considerable variability in density values even within individual rock types. As expected, rocks containing higher proportions of ferromagnesian minerals (i.e., basalt, diorite, and gabbro) generally gave higher magnetic susceptibility values. The lack of aeromagnetic anomalies over mafic volcanic rocks in the central Caledonia Highlands may possibly be explained in terms of thin and flat-lying flow units.

scholarly journals Interpretation of shallow electromagnetic instruments resistivity and magnetic susceptibility measurements using rapid 1D/3D inversion

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. E103-E112 ◽  
Author(s):  
Christophe Benech ◽  
Michel Dabas ◽  
François-Xavier Simon ◽  
Alain Tabbagh ◽  
Julien Thiesson
Keyword(s):  
Magnetic Susceptibility ◽  
Synthetic Data ◽  
Low Frequency ◽  
Test Site ◽  
3D Inversion ◽  
Magnetic Susceptibility Data ◽  
Susceptibility Data ◽  
Surface Areas ◽  
Instrument Configuration

We have developed an inversion process of electromagnetic induction (EMI) data based on a two-step approach with 1D inversion of the entire studied surface and a fast 3D inversion applied over limited areas. This process is similar to that formerly used in resistivity prospection. For the study of soil (environmental, engineering, or archaeological explorations), low-frequency electromagnetic instruments (referred to as Slingram EMI) have highly useful specificities. They are light, are easy to move in the field, and can simultaneously measure the ground’s electric conductivity and magnetic susceptibility; they have thus been used to map these properties over large surface areas, within relatively short periods of time, and at reasonable expense. The possibility of combining several coil geometries has opened up the potential for multidepth techniques and systematic 1D inversion, which are found to be sufficiently revealing to allow larger portions of surveyed areas to be analyzed. In the “targeted areas” selected for 3D inversion, the geometries of the 3D features and the resistivity and/or susceptibility contrasts are determined. This step is based on the method of moments, where only 3D heterogeneities are meshed, and only a small number of major characteristics, such as contrast, thickness, width, etc., are sought. We first applied this process to synthetic data, then to data acquired at an experimental test site, and finally to field cases. The rapid 3D inversion complements the 1D inversion by solving a series of issues: correction for the apparent anisotropy generated by the instrument configuration, multiarched anomalies, precise location of lateral changes, and determination of the properties contrasts. Our inversion results highlighted the importance of the instrument geometry. We also have determined that apparent magnetic susceptibility data can be more appropriate for the determination of the volume of man-made features and can be highly complementary to conductivity data.

scholarly journals Geochronology of the Neogene calc-alkaline intrusive magmatism in the "Subvolcanic Zone" of the Eastern Carpathians (Romania)

2009 ◽  
Vol 60 (2) ◽  
pp. 181-190 ◽  
Author(s):  
Zoltán Pécskay ◽  
Ioan Seghedi ◽  
Marinel Kovacs ◽  
Alexandru Szakács ◽  
Alexandrina Fülöp
Keyword(s):  
Volcanic Rocks ◽  
Magmatic Evolution ◽  
Calc Alkaline ◽  
Geodynamic Evolution ◽  
Reciprocal Relationships ◽  
Tectonic Processes ◽  
Eastern Carpathians ◽  
Wide Range ◽  
Intrusive Rocks ◽  
Intrusive Activity

Geochronology of the Neogene calc-alkaline intrusive magmatism in the "Subvolcanic Zone" of the Eastern Carpathians (Romania)The Poiana Botizei-Ţibleş-Toroiaga-Rodna-Bârgâu intrusive area (PBTTRB), northwest Romania, known as the "Subvolcanic Zone", is located between the Gutâi (NW) and Câlimani (SE) volcanic massifs. It consists of rocks displaying a wide range of compositions and textures: equigranular or porphyritic with holocrystalline groundmass (gabbro-diorites, diorites, monzodiorites and granodiorites), and/or porphyritic with fine holocrystalline or glassycryptocrystalline groundmass, similar with effusive rocks: basalts, basaltic andesites, andesites, dacites and rhyolites. The time-span of intrusive rocks emplacement is similar with the nearest calc-alkaline volcanic rocks from Gutâi (NW) and Câlimani (SE) massifs. They are represented by stocks, laccoliths, dykes and sills typical for an upper crustal intrusive environment. In the absence of biostratigraphic evidence, a comprehensive K-Ar study of intrusive rocks using whole rock samples, groundmass and monomineral fractions (biotite, hornblende) has been carried out in order to understand the magmatic evolution of the area. The oldest K-Ar ages recorded in the analysed rocks are close to 11.5 Ma and magmatism continued to develop until about 8.0 Ma. The inception of intrusion emplacement in the PBTTRB is coeval with intrusive activity spatially related to volcanism within the neighbouring Gutâi and Câlimani massifs. However, its culmination at ca. 8 Ma ago is younger than the interruption of this activity at ca. 9.2 Ma in Gutâi and Câlimani Mts where intrusive activity resumed for ca. 1 Myr. These circumstances strongly suggest that the geodynamic evolution of the area controlled the development of both volcanic and intrusive activity and their reciprocal relationships. The overall geological data suggest that in the PBTTRB intra-lithospheric transpressional-transtensional tectonic processes controlled the generation and emplacement of intrusive bodies between ca. 12-8 Ma.

scholarly journals Analisis Anisotropi Suseptibilitas Magnetik Batuan Beku Lengan Utara Sulawesi

Jurnal MIPA ◽  
2017 ◽  
Vol 6 (1) ◽  
pp. 8 ◽  
Author(s):  
Melisa Rongkonusa ◽  
Gerald Tamuntuan ◽  
Guntur Pasau
Keyword(s):  
Magnetic Susceptibility ◽  
Igneous Rock ◽  
Anisotropy Of Magnetic Susceptibility ◽  
Igneous Rocks ◽  
North Sulawesi ◽  
Intrusive Rocks ◽  
The Status ◽  
Melting Mechanism

Telah dilakukan  penelitian untuk menentukan pola anisotropi suseptibilitas magnetik dan status singkapan batuan beku dari pola yang diperoleh. Pengukuran anisotropi suseptibilitas magnetic dilakukan pada lima sampel batuan beku dari Sulawesi Utara menggunakan Bartington MS2B. Arah pengukuran sampel disesuaikan dengan desain Tauxe. Hasilnya menunjukkan bahwa suseptibilitas maksimum terdistribusi disekitar  arah  utara dan timur. Sedangkan suseptibilitas intermediet dan minimum terdistribusi disekitar Utara-Timur dan Timur-Selatan. Elipsoida suseptibilitas  cenderung  prolate atau lebih lonjong. Batuan beku yang dianalisis merupakan kelompok batuan terobosan yang mekanisme lelehannya terjadi secara vertikal.A research has been conducted to determine the anisotropic pattern of magnetic susceptibility and the status of igneous rocks exposure from the obtained pattern. We have measured the anisotropy of magnetic susceptibility on five samples of igneous rock from North Sulawesi by Bartington MS2B. The position of samples were adjusted according to the Tauxe’s design. The result shows that the maximum susceptibility is distributed around northward and eastward, while the intermediate and minimum susceptibility are distributed around nortward-eastward and eastward-southward. The susceptibility ellipsoid tends to be prolate or more oval. This shows that the igneous rocks that have been analyzed are group of intrusive rocks which melting mechanism occurs through vertical fracture.enetie

LOW‐AMPLITUDE AEROMAGNETIC ANOMALIES IN SOUTHEASTERN MISSOURI

Geophysics ◽  
1964 ◽  
Vol 29 (4) ◽  
pp. 537-552 ◽  
Author(s):  
John W. Allingham
Keyword(s):  
Volcanic Rock ◽  
Mineral Exploration ◽  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Aeromagnetic Anomalies ◽  
Fine Grained ◽  
Mining Areas ◽  
Granite Batholith ◽  
Extrusive Rock ◽  
Low Amplitude

This study shows that aeromagnetic anomalies of less than 200 gammas are associated with topographic relief of exposed Precambrian granitic and volcanic rocks of the St. François Mountains. Anomalies resulting from hills coarsely crystalline granite are as high as 100 gammas in amplitude, whereas anomalies over comparable hills of fine‐grained rocks, such as granophyre or devitrified volcanic rock, are as much as 200 gammas. Anomalies caused by normal faulting or shearing of igneous rocks have amplitudes of less than 100 gammas; they are observed best in profile. These anomalies are superposed on larger magnetic features related to pendants of volcanic rock in the roof of a granite batholith and are distinguished from large lateral variations in magnetic intensity by their low amplitude and small areal extent. Analyses of the compound anomalies yielded the subsurface configuration of isolated roof pendants of resistant extrusive rock in some areas. As many of these pendants have negligible remanent magnetization, induction theory was used in the analyses. Application of these results to the lead‐mining areas shows that aeromagnetic patterns of low amplitude can guide mineral exploration in the region flanking the Ozark uplift, where isolated, buried hills of Precambrian igneous rocks controlled the development of some lead‐bearing sedimentary structures in the overlying Cambrian carbonate strata.

scholarly journals LA-ICP-MS U-Pb apatite dating of Lower Cretaceous rocks from teschenite-picrite association in the Silesian Unit (southern Poland)

2014 ◽  
Vol 65 (4) ◽  
pp. 273-284 ◽  
Author(s):  
Krzysztof Szopa ◽  
Roman Włodyka ◽  
David Chew
Keyword(s):  
Volcanic Activity ◽  
Volcanic Rocks ◽  
Weighted Average ◽  
Magmatic Rocks ◽  
Three Samples ◽  
Icp Ms ◽  
Outer Western Carpathians ◽  
Wide Range ◽  
Igneous Province ◽  
Intrusive Rocks

Abstract The main products of volcanic activity in the teschenite-picrite association (TPA) are shallow, sub-volcanic intrusions, which predominate over extrusive volcanic rocks. They comprise a wide range of intrusive rocks which fall into two main groups: alkaline (teschenite, picrite, syenite, lamprophyre) and subalkaline (dolerite). Previous 40Ar/39Ar and 40K/40Ar dating of these rocks in the Polish Outer Western Carpathians, performed on kaersutite, sub-silicic diopside, phlogopite/biotite as well as on whole rock samples has yielded Early Cretaceous ages. Fluorapatite crystals were dated by the U-Pb LA-ICP-MS method to obtain the age of selected magmatic rocks (teschenite, lamprophyre) from the Cieszyn igneous province. Apatite-bearing samples from Boguszowice, Puńców and Lipowa yield U-Pb ages of 103± 20 Ma, 119.6 ± 3.2 Ma and 126.5 ± 8.8 Ma, respectively. The weighted average age for all three samples is 117.8 ± 7.3 Ma (MSWD = 2.7). The considerably smaller dispersion in the apatite ages compared to the published amphibole and biotite ages is probably caused by the U-Pb system in apatite being less susceptible to the effects of hydrothermal alternation than the 40Ar/39Ar or 40K/40Ar system in amphibole and/or biotite. Available data suggest that volcanic activity in the Silesian Basin took place from 128 to 103 Ma with the the main magmatic phase constrained to 128-120 Ma.

Carboniferous volcanic rocks of the Magdalen Islands, Gulf of St. Lawrence

1985 ◽  
Vol 22 (11) ◽  
pp. 1679-1688 ◽  
Author(s):  
Sandra M. Barr ◽  
Daniel Brisebois ◽  
Alan S. Macdonald
Keyword(s):  
Iron Oxides ◽  
Volcanic Rocks ◽  
Potassium Feldspar ◽  
Igneous Rocks ◽  
Chemical Compositions ◽  
Mafic Dykes ◽  
Basaltic Rocks ◽  
Wide Range ◽  
Volcaniclastic Deposits ◽  
Magdalen Islands

Volcanic rocks of Mississippian age occur on the Magdalen Islands as cap rocks and within collapse breccias above salt diapirs that have formed the islands. They consist of coarse volcaniclastic deposits and basaltic flows, intruded by minor mafic dykes and plugs. Petrologic studies of the basaltic rocks show that they are extensively altered. Original plagioclase, clinopyroxene, olivine, and interstitial glass are partially to entirely replaced by mixtures of chlorite, sericite, smectite, sphene, carbonate, epidote, albite, potassium feldspar, and iron oxides, and the samples display a relatively wide range in chemical compositions. Especially mobile were K, Na, and Ca, and most samples are classified as potash spilites (poenites). Using standard discriminant diagrams for mafic igneous rocks, it can be seen that the basalts appear to range from continental tholeiitic to continental alkalic. However, relict clinopyroxene compositions and the presence of kaersutitic amphibole and titaniferous biotite in some samples imply that the suite may originally have been more alkalic than tholeiitic.

scholarly journals Unravelling the internal architecture of the Alnö alkaline and carbonatite complex (central Sweden) using 3D models of gravity and magnetic data

2017 ◽  
Author(s):  
Magnus Andersson ◽  
Alireza Malehmir
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic Anomaly ◽  
Bouguer Anomaly ◽  
Magnetic Data ◽  
Common Source ◽  
Gravity Gradients ◽  
Aeromagnetic Data ◽  
3D Inversion ◽  
Gravity And Magnetic ◽  
Magnetic Inversion

Abstract. The Alnö complex in central Sweden is one of the largest alkaline and carbonatite ring-shaped intrusions in the world. Presented here is the 3D inversion of ground gravity and aeromagnetic data that confirms some of the previous ideas about the 3D geometry of the complex but also suggests that the complex may continue laterally further to north than earlier expected. The gravity and aeromagnetic data show the complex as (i) a strong positiver Bouguer anomaly, around 20 mGal, one of the strongest gravity gradients observed in Sweden, and (ii) a strong positive magnetic anomaly, exceeding 2000 nT. Magnetic structures are clearly discernible within the complex and surrounding area. Petrophysical measurements (density, bulk magnetic susceptibility, and magnetic remanence) were used to constrain the 3D inversion. Both gravity and magnetic inversion models suggest that dense (> 2850 kg/m3) and magnetic (> 0.05 SI) rocks extend down to about 3.5–4 km depth. Previous studies have suggested a solidified magma reservoir at this approximate depth. The inversion models further suggest that two apparently separate regions within the intrusion with gravity and magnetic highs are likely connected at depth, starting from 800–1000 m, implying a common source for the rocks observed in these two regions. The modelling of the aeromagnetic data indicates that a more than 3 km wide ring-shaped magnetic high in the bay that can be a hidden part of the complex, linking a satellite intrusion in Söråker on the northern side of the bay to the main intrusion on the Alnö Island. While the rim of the ring must consist of highly susceptible rocks to support the magnetic anomaly, the centre has a relatively low magnetisation and is probably made up of low-susceptible wall-rocks or metasomatised wall-rocks down to about 2 km. Below this depth the 3D susceptibility model shows higher magnetic susceptibility values. From these observations the solidified magma chamber is interpreted to extend further to north than has previously been suggested.

REMANENT MAGNETISM AS A CONTRIBUTOR TO SOME AEROMAGNETIC ANOMALIES

Geophysics ◽  
1962 ◽  
Vol 27 (3) ◽  
pp. 359-375 ◽  
Author(s):  
Kenneth G. Books
Keyword(s):  
Remanent Magnetization ◽  
Volcanic Rocks ◽  
Horizontal Direction ◽  
Dominant Factor ◽  
Rock Body ◽  
North Central ◽  
Remanent Magnetism ◽  
Aeromagnetic Anomalies ◽  
Intrusive Rocks ◽  
Central Montana

An investigation of some aeromagnetic anomalies in north‐central Montana shows that remanent magnetization is the dominant factor in anomalies over some rocks and a contributing factor in anomalies over others. In volcanic rocks, remanence is commonly south‐seeking down and has an intensity approximately ten times the induced intensity of magnetization. Remanence is shown to be the dominating factor in anomalies over volcanic rocks by the agreement between the profiles of an observed anomaly over a volcanic rock body and an anomaly calculated from remanence data for the same body. In intrusive rocks, the remanence is north‐seeking down and comparable in intensity to the induced intensity of magnetization. That remanence also contributes to the anomalies over some intrusive rocks is shown by the agreement between the profiles of an observed anomaly over an intrusive body and an anomaly calculated from the resultant of induced and remanent magnetizations. A consistent relationship between the axis of the anomaly, or direction between the anomaly high and low, and the horizontal direction of magnetization suggests that the direction of the anomaly axis can be used to indicate the horizontal direction of magnetization in this area.

scholarly journals Volcanic reservoirs: historic and current context

2021 ◽  
Vol 48 (1) ◽  
pp. e104451
Author(s):  
Patricia Lopes DESCOVI ◽  
Marcus Vinícius Berao ADE ◽  
Gabriela De Oliveira AVELLAR ◽  
Silvia Lorena Bejarano BERMÚDEZ ◽  
Fábio Pinto VIEIRA
Keyword(s):  
Oil And Gas ◽  
Volcanic Rocks ◽  
Historical Review ◽  
Oil And Gas Industry ◽  
Igneous Rocks ◽  
Daily Production ◽  
Gas Industry ◽  
Wide Range ◽  
The World ◽  
Volcanic Reservoirs

Within the oil and gas industry, igneous rocks are still seen as exploration and production challenges, due to their diverse petrogenesis and the wide range of values of some important petrophysical properties. This petrophysical variability depends on both primary and secondary processes. These facts made these rocks unattractive for decades. This condition is still observed in many fields around the world. This article has as main objective to make a historical review of studies developed globally with a focus on igneous rocks that act as a reservoir in petroleum systems. The review covered in this article was developed from a compilation of global data, thus allowing an overview of the countries that produce hydrocarbons in volcanic rocks, what types of rocks, geological age, and size of the reserve. Countries such as China and Indonesia stand out with higher daily production, exceeding orders of quantities of 108 cubic meters of gas and 104 tons of barrels of oil. In these countries, geological patterns are already being noticed in volcanic reservoirs, such as more recent geological ages and typical lithologies. Also, this work seeks to emphasize the importance of studying this type of reservoir, as its knowledge can lead to the solution of real problems within the world oil and gas industry.

Sign in / Sign up

Export Citation Format

Share Document