Magma Flow Directions in Dikes of the Koolau Complex, Oahu, Determined From Magnetic Fabric Studies

2014 ◽  
pp. 4301-4319
Author(s):  
Michael D. Knight ◽  
George P. L. Walker
Keyword(s):  
Magnetic Fabric ◽  
Magma Flow ◽  
Flow Directions

Magma flow directions inferred from field evidence and magnetic fabric studies of the Streitishvarf composite dike in east Iceland

2011 ◽  
Vol 206 (1-2) ◽  
pp. 30-45 ◽  
Author(s):  
Per I. Eriksson ◽  
Morten S. Riishuus ◽  
Freysteinn Sigmundsson ◽  
Sten-Åke Elming
Keyword(s):  
Magnetic Fabric ◽  
Magma Flow ◽  
Field Evidence ◽  
Flow Directions

Magnetic fabric and flow directions in magmatic rocks of the Franz Josef Land, Arctic Ocean

2020 ◽  
Author(s):  
Anna Chernova ◽  
Viktor Abashev ◽  
Dmitry Metelkin ◽  
Valery Vernikovsky ◽  
Nikolay Mikhaltsov
Keyword(s):  
Lava Flow ◽  
Complex Analysis ◽  
Flow Direction ◽  
Lava Flows ◽  
Magnetic Fabric ◽  
Basaltic Lava ◽  
Magma Flow ◽  
Franz Josef Land ◽  
Degree Of Anisotropy ◽  
Flow Directions

<p>Here, we present the results of a study of the anisotropy of magnetic susceptibility (AMS) completed in the Early Cretaceous magmatic complexes from the Franz Josef Land (FJL). AMS was measured in the framework of paleomagnetic research as a leading indicator of the rock magnetic fabric to help in understanding the lava flow directions and forming mechanisms. The three types of magmatic bodies were available in these studies: dolerite sills, dykes and basaltic lava flows from several islands (Alexandra, Hall, Ziegler, Jackson and Heiss Islands) among FJL. During the experiments the different parameters of AMS ellipsoids were obtained which have a good correlation with the igneous body shapes and also could illustrate lava flows direction parameters. The degree of anisotropy P is 1.01-1.06 for most sites that is typical for the primary igneous magnetic fabric. The form factor T characterizing the shape of the AMS ellipsoids demonstrates both planar and linear magnetic fabric in studied magmatic bodies. What is remarkable the part of the dykes is characterized strictly oblate magnetic fabric and another dykes have the prolate AMS ellipsoids. The linear magnetic structure is also more typical for lava flows with the maximum axes K1 lying in the flow plane that is obviously could point to the flow direction. The part of the igneous bodies are characterized by the inverse type of magnetic fabric, when the principal axis K1 of the ellipsoid is oriented perpendicularly to the plane of the flow or the sill, that was likely caused by the effect of secondary processes. The previous studies (Abashev et al., 2019) demonstrated that the primary orientation of the AMS ellipsoid could be recovered after temperature demagnetization. Noticeable changes were revealed at heating up to ~450 deg C, which generally corresponds to deblocking temperatures of titanomagnetites identified in the rocks by rock-magnetic methods. The degree of anisotropy was decreased after heating in 2-3 times. The heating also resulted to the redistribution of magnetic axes and in several cases the axes becomes more grouped. Analysis of the AMS results from the basaltic lava flows of the Aleksandra Island defined the magma flow direction to be NW-SE. Similar behavior of the AMS ellipsoids and lava flow orientation is typical for Ziegler Island. Generally our results show that complex analysis of AMS data in basaltic rocks is promising for identifying magma flow direction and it can give more detailed information about forming mechanisms of the different magmatic bodies.</p><p>This work was supported by the RSF (project no. 19-17-00091) and the RFBR (project nos. 18-35-00273, 18-05-70035).</p>

Magma flow directions of shallow dykes from the East Greenland volcanic margin inferred from magnetic fabric studies

2001 ◽  
Vol 335 (3-4) ◽  
pp. 313-329 ◽  
Author(s):  
J.-P Callot ◽  
L Geoffroy ◽  
C Aubourg ◽  
J.P Pozzi ◽  
D Mege
Keyword(s):  
Magnetic Fabric ◽  
Magma Flow ◽  
East Greenland ◽  
Volcanic Margin ◽  
Flow Directions

Anisotropy of magnetic susceptibility in alkaline-ultramafic dikes of the Kotuy river valley: Reconstruction of magma transport during the Siberian Traps emplacement

2020 ◽  
Author(s):  
Anton Latyshev ◽  
Victor Chmerev ◽  
Victor Zaitsev
Keyword(s):  
River Valley ◽  
Magnetic Fabric ◽  
Ultramafic Rocks ◽  
Limited Area ◽  
Magmatic Activity ◽  
Contact Zones ◽  
Magma Flow ◽  
Siberian Traps ◽  
Magmatic Stage ◽  
Alkaline Lamprophyres

<p>Products of the Permian-Triassic magmatic activity in the Kotuy river valley consist of two contrasting in composition groups: 1) tholeiitic basalts, similar to the main volume of the Siberian Traps; 2) alkaline-ultramafic rocks which are extremely rare in other regions of the Siberian platform. Alkaline lavas and tuffs in the Kotuy river valley are exposed only in limited area (Arydzhangsky and Khardakhsky formations), however, multiphase circular plutons (Kugda, Odikhincha) and swarms of radial and parallel dikes marks the essentially wider territory of the manifestation of alkaline magmatic activity.</p><p>Here we present the preliminary results of the investigation of AMS in the dike complex of alkaline lamprophyres from the Kotuy river valley. The majority of dikes demonstrate I-type of the magnetic fabric, when the medium axes K2 of AMS ellipsoid is orthogonal to the contact of intrusion. In dikes where the minimal axis K3 is subvertical and maximal axis K1 is flat, we interpret this magnetic fabric as a result of cooling of the static magma column after the emplacement in the setting of horizontal extension (Park et al., 1988; Raposo and Ernesto, 1995). Also, N-type and R-type of magnetic fabric were identified as well. In some intrusions, the orientation of the axes of AMS ellipsoid changes from the contact zones to the inner part if intrusion. In this case, we used data from the contact zones for the magma flow reconstruction.</p><p>Analysis of the maximal axis K1 orientation in different dikes showed that in majority of bodies it shallowly plunges to the west. This corresponds to the lateral magma flow from west to east during the emplacement. Consequently, formation of the studied dikes is not directly related to Kugda pluton, which is located 8 km eastward. The emplacement of dikes occurred from the magmatic center located westward from the Kotuy river valley and is not associated with any known large massifs. Petrographic similarity of the studied dikes to the lavas of Arydzhangsky formation allows us to suggest that they are coeval. This implies the wider area of manifestation of the Arydzhangsky magmatic stage.</p><p>This work was supported by RFBR (projects 18-35-20058, 18-05-70094, 17-05-01121 and 20-05-00573).</p>

Magnetic fabric and tectonic setting of the Early to Middle Jurassic felsic dykes at Pitt Point and Mount Reece, eastern Graham Land, Antarctica

2011 ◽  
Vol 24 (1) ◽  
pp. 45-58 ◽  
Author(s):  
Jiří Žák ◽  
Igor Soejono ◽  
Vojtěch Janoušek ◽  
Zdeněk Venera
Keyword(s):  
Stress Field ◽  
Middle Jurassic ◽  
Large Scale ◽  
Tectonic Setting ◽  
Local Stress ◽  
Weddell Sea ◽  
Magnetic Fabric ◽  
Magma Source ◽  
Magma Flow ◽  
North Eastern

AbstractAt Pitt Point, the east coast of Graham Land (Antarctic Peninsula), the Early to Middle Jurassic (Toarcian–Aalenian) rhyolite dykes form two coevally emplaced NNE–SSW and E–W trending sets. The nearly perpendicular dyke sets define a large-scale chocolate-tablet structure, implying biaxial principal extension in the WNW–ESE and N–S directions. Along the nearby north-eastern slope of Mount Reece, the WNW–ESE set locally dominates suggesting variations in the direction and amount of extension. Magnetic fabric in the dykes, revealed using the anisotropy of magnetic susceptibility (AMS) method, indicates dip-parallel to dip-oblique (?upward) magma flow. The dykes are interpreted as representing sub-volcanic feeder zones above a felsic magma source. The dyke emplacement was synchronous with the initial stages of the Weddell Sea opening during Gondwana break-up, but it remains unclear whether it was driven by regional stress field, local stress field above a larger plutonic body, or by an interaction of both.

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