Magnetic susceptibility and geochemistry of Variscan West Carpathian granites: implications for tectonic setting

Gregorová, Dagmar; Hrouda, František; Kohút, Milan

doi:10.1016/s1474-7065(03)00125-6

Cited by 16 publications

(7 citation statements)

References 8 publications

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“…Whereas the magnetic susceptibility begins to increase when the temperature is up to 300 • C, and the curve sharply drops when the temperature is high up to 580 • C, so the obvious Hopkinson effect can be observed in Fig. 2b, which indicates the presence of magnetite grains during the heating process [23,24] because of the typical Curie point as 575 • C∼585 • C of magnetite [22] . And then magnetic susceptibility has an apparent decrease at the vicinity of temperature of 670 • C, which reflects the existence of magnetite [25] .…”

Section: Magnetic Mineralmentioning

confidence: 96%

Characteristics of Magnetic Fabric of Wenquan Granite Pluton in the Western Qinling Mountains and Implications for Emplacement Mechanism

Xie¹,

Zhang²,

Lu³

et al. 2010

Chinese J of Geophysics

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Wenquan pluton is situated in the western Qinling mountains and is adjacent to the south of the Shangdan suture zone. Through analyses of regional tectonics and the anisotropy of low‐field magnetic susceptibility (AMS) together with rock magnetism of 125 oriented samples, the emplacement mechanism of the pluton is studied. The values of most mean susceptibilities (km) show a wide variation range. Thermomagnetic curves demonstrate that the paramagnetic minerals such as biotite, acting as the main magnetic carriers, made dominant contributions to the magnetic susceptibility of the samples with low values, also including a small contribution to remanence from small amount of magnetite. The magnetite, however, acted as the dominant magnetic carrier of the samples with high magnetic susceptibility values. The corrected anisotropy degree (PJ ) less than 1.2 can be regarded as flow magnetic fabrics based on microscopic observations. The shape parameters (T) of most of magnetic susceptibility ellipsoid display that the Wenquan pluton is dominated by oblate compressional fabric, and the magnetic foliations are dominant over magnetic lineations. In addition, it is well marked that most magnetic foliations of the samples on the border seem parallel to the edge of the granite pluton, which have relatively steep inclinations, and interior ones appear relatively disordered besides magnetic lineations. Hence it can be revealed that the magnetic fabrics of the pluton are mainly formed by the lateral compression during the emplacement. Though the magnetic fabrics show N‐NEE and SW directed compression as a whole, the compression caused by the closure of the Shangdan suture zone during the Indo‐China period became much weaker than that in the main orogenic stage. Consequently it can be concluded that the weak compression setting can be reflected by the characteristics of magnetic fabrics when the pluton emplaced, and furthermore the relatively sustained and even extensional environment was probable and understandable, which was consistent with the regional tectonic setting in the extension stage of the emergence of delamination when the Qinling orogenic belt evolved to post‐collision stage.

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Section: Magnetic Mineralmentioning

confidence: 96%

Characteristics of Magnetic Fabric of Wenquan Granite Pluton in the Western Qinling Mountains and Implications for Emplacement Mechanism

Xie¹,

Zhang²,

Lu³

et al. 2010

Chinese J of Geophysics

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“…The magnitudes of magnetic susceptibility and remanent magnetic polarization (RMP) were assessed. Magnetic properties are given in the Table 1, according to data given by Husák & Stránska (1980), Grecula & Kucharič et al (1985 and Gregorová et al (2003). Variability in the parameters under study is obvious (this is the typical feature of magnetic rocks) and therefore the significance of average values is only on the informative level.…”

Section: Magnetic Properties Of Minerals and Rocksmentioning

confidence: 99%

Magnetic field of the Western Carpathians (Slovakia): reflections on the structure of the crust

Kubeš¹,

Bezák²,

Kucharič³

et al. 2010

Geologica Carpathica

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Abstract:A new digital magnetic map of Slovakia on the scale of 1: 200,000 and 1: 500,000 was compiled at the end of 2008 as the output of database magnetic objects from the whole territory of Slovakia at a scale of 1: 50,000. The variable geological structure of the West Carpathian crust is depicted in the equally variable magnetic field of this region. A sizable number of magnetic anomalies with manifold character have been recognized. The basic anomalies distribution was divided into two groups: anomalies connected with rocks of the pre-Neogene basement and anomalies which originate in Neogene and Quaternary volcanic products. Most of the significant anomalies in the pre-Neogene basement were interpreted, modelled and consequently its geological and tectonic classification was worked out. On the basis of the anomalous field features, the following sources of anomalies have been distinguished: a) known, located on the surface, or at shallow depths verified by boreholes, mainly expressed by simple morphology, b) deep-seated and expressed by complicated morphology, reinterpreted or newly interpreted and also problematic. According to our present knowledge the interpretations are insufficient and remain open for further investigation. The above mentioned sources of magnetic anomalies are classified in terms of tectonic provenience to the main tectonic units.

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“…Granites ( s.l .) are commonly bimodal in nature and in petrophysical terms can be grouped as magnetic or ferromagnetic and weakly magnetic or paramagnetic depending upon the relative modal amount of magmatic opaque minerals viz., magnetite ± ilmenite in metaluminous (I‐type) and ilmenite + sulphide ± magnetite in peraluminous (S‐type) granites (Gregorová et al, 2003; Kumar, 2008 and references therein). The degree of magnetization of a material in response to the presence or absence of magnetic minerals can be measured in terms of magnetic susceptibility (MS) value (×10 −3 SI unit), which provides an approximate indicator of granite origin (e.g., Ellwood & Wenner, 1981).…”

Section: Introductionmentioning

confidence: 99%

“…The MS values (×10 −3 SI unit) can be used as an index to differentiate the granitic rocks into two series viz., the magnetite series (MS ≥3.0 × 10 −3 SI units) and the ilmenite series (MS ≤3.0 × 10 −3 SI units) granites (Ishihara, 1977). However, as the occurrence of magnetite or ilmenite is primarily controlled by the oxygen fugacity of the magma source, the correlation between the granite types and granite series need not to be very close (Gregorová et al, 2003). In addition, the magnetic mineral assemblage may reflect not only the conditions of granite formation, but also the processes of its later evolution whereby its magnetic mineralogy might have been changed (Gregorová et al, 2003 and references therein).…”

Section: Introductionmentioning

confidence: 99%

Magnetic susceptibility, mineral chemistry, and geothermobarometry of granitoids from Lohit Plutonic Complex, Arunachal Trans‐Himalaya, Northeast India: Implications on emplacement and crystallization conditions of oxidized calc alkaline magmatic arc system

et al. 2023

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The Lohit Plutonic Complex (LPC) of Arunachal Trans‐Himalaya represents the northeast extension of Trans‐Himalayan magmatic arc system located in the north of Indus Tsangpo Suture Zone (ITSZ). Field relation, magnetic susceptibility (MS), and phase petrology on the granitoids of LPC was conducted in order to assess the granite series (magnetite, oxidized vs. ilmenite, reduced types), and physico‐chemical conditions of the LPC granitoid magmas. The studied granitoids are well‐exposed in the Dibang and Lohit valleys, and their MS values indicate a bi‐modal patterns corresponding to ilmenite (reduced) series (71%) and magnetite (oxidized) series (29%) granites. The variation of MS in the LPC granitoids is related to the alteration of ferromagnetic minerals, and later tectonic and deformational processes that acted upon them. The amphiboles from the LPC granitoids are calcic (CaB >1.5, Si = 6.30–7.06 apfu) and exhibit tschermak substitutions typical to their evolution in a calc alkaline, metaluminous (I‐type) felsic magmas. Al‐in‐hornblende rims estimate the emplacement of quartz diorite and granodiorite magmas at shallow (~5 km) and mid (~16 km) crustal depths. Geothermometric results point to a regime of magmatic crystallization (940–837°C for quartz diorite; 882–829°C for granodiorite) sufficiently above the solidus of respective melts. Biotites from LPC granitoids are primary to re‐equilibrated, and transitional between magnesio‐ and ferri‐biotites. Quartz diorite and granodiorite biotites evolved under oxidizing magmas (log ƒO2−14 to log ƒO2−13) in a temperature range of ~750–950°C, typical to their formation in a calc alkaline magma of subduction zone environment. However, the biotites from leucogranite appear to have evolved under a mildly reducing magma environment, most likely attained in a collisional setting. The obtained results suggest that the oxidized nature of calc alkaline, subduction‐related magmatic arc rocks of the LPC is largely modified and reduced by post‐magmatic, and later tectonothermal and deformational events that operated during Himalayan and Trans‐Himalayan orogenesis.

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Magnetic susceptibility and geochemistry of Variscan West Carpathian granites: implications for tectonic setting

Cited by 16 publications

References 8 publications

Characteristics of Magnetic Fabric of Wenquan Granite Pluton in the Western Qinling Mountains and Implications for Emplacement Mechanism

Characteristics of Magnetic Fabric of Wenquan Granite Pluton in the Western Qinling Mountains and Implications for Emplacement Mechanism

Magnetic field of the Western Carpathians (Slovakia): reflections on the structure of the crust

Magnetic susceptibility, mineral chemistry, and geothermobarometry of granitoids from Lohit Plutonic Complex, Arunachal Trans‐Himalaya, Northeast India: Implications on emplacement and crystallization conditions of oxidized calc alkaline magmatic arc system

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