Late Holocene Malpaís de Zacapu (Michoacán, Mexico) andesitic lava flows: rheology and eruption properties based on LiDAR image

The Amisk Group (Aphebian?) near Flin Flon, Manitoba, consists dominantly of andesitic lava flows and pyroclastic rocks, with minor basalt, dacite, rhyolite, and epiclastic rocks. These have undergone regional metamorphism ranging from chlorite to garnet zone, and locally have been sheared intensely.Major element chemical analyses indicate that intensely sheared Amisk rocks near the Flin Flon and Schist Lake Cu–Zn ore bodies have undergone considerable metasomatism. The unsheared, regionally metamorphosed rocks have undergone significantly less metasomatism, and the compositions of the least-altered of these suggest an island arc tholeiite chemical affinity.The lithology, primary structures, and major-element compositions of lavas within the Amisk Group suggest deposition may have been in an island arc environment.

Download Full-text

Upper Cretaceous Stratigraphy and Volcanism in the İğneada region, Pontides, NW Turkey

10.5194/egusphere-egu2020-8519 ◽

2020 ◽

Author(s):

Ezgi Sağlam ◽

Turgut Duzman ◽

Aral I. Okay

Keyword(s):

Upper Cretaceous ◽

Planktonic Foraminifera ◽

Lava Flows ◽

Arc Volcanism ◽

Magmatic Arc ◽

Andesitic Lava ◽

Black Sea Coast ◽

Nw Turkey ◽

Sandy Limestone ◽

Volcaniclastic Rocks

The Pontide Upper Cretaceous magmatic arc can be traced for over 1000 km along the southern Black Sea coast from Georgia to Bulgaria. &#160;The arc extrusive sequence is well-exposed in the &#304;&#287;neada region in Thrace close to the Bulgarian border. The Upper Cretaceous sequence in &#304;&#287;neada region overlies the schists and phyllites of Strandja Massif with an unconformity. It &#160;has a thickness of over 700 meters and consists at the base of Cenomanian shallow marine sandy limestone, which pass up into pelagic limestone, marn and volcanogenic siltstone with Turonian planktonic foraminifera, including Marginotruncana pseudolinneana, Marginotruncana marginata, Whitenella sp., Whitenella praehelvetica, Muricohedbergella sp.&#160; This indicates that the arc volcanism in the region started in the Turonian. The pelagic limestone, marl, and calcareous siltstone series passes up into a volcanic-volcaniclastic sequence of andesitic tuff, lapillistone, agglomerate, andesitic and basaltic-andesitic lava flows. The volcaniclastic rocks are intercalated with lava flows and with rare pelagic limestone and shale beds. Although it is disrupted by several faults, the volcanic sequence can be traced from older to younger along the coast of &#304;&#287;neada. The sequence starts with andesitic volcaniclastic rocks and lava flows, and changes to basaltic-andesitic and then, again to andesitic rocks. The ocean floor alteration, which is found in all volcaniclastic and volcanic rock samples, and the intercalated pelagic limestones show that the rocks were deposited in deep submarine conditions in an intra-arc to fore-arc environment. Campanian (80.6 &#177;1.5 Ma) U-Pb zircon ages, which are obtained from the andesitic tuffs at the base of the volcanic-volcaniclastic sequence, indicate a continued magmatism from Turonian to Campanian.

Download Full-text

Post-emplacement dynamics of andesitic lava flows at Volcán de Colima, Mexico, revealed by radar and optical remote sensing data

Journal of Volcanology and Geothermal Research ◽

10.1016/j.jvolgeores.2019.05.019 ◽

2019 ◽

Vol 381 ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

Alexandre Carrara ◽

Virginie Pinel ◽

Pascale Bascou ◽

Emmanuel Chaljub ◽

Servando De la Cruz-Reyna

Keyword(s):

Remote Sensing ◽

Remote Sensing Data ◽

Lava Flows ◽

Optical Remote Sensing ◽

Volcán De Colima ◽

Sensing Data ◽

Andesitic Lava ◽

Volcan De Colima

Download Full-text

Anisotropy of magnetic susceptibility (AMS) of lava and volcanoclastic flows of the Stephano-Permian Cadi basin (central-eastern Pyrenees)

10.5194/egusphere-egu2020-10284 ◽

2020 ◽

Author(s):

Ana Simon-Muzas ◽

Antonio M Casas-Sainz ◽

Ruth Soto ◽

Josep Gisbert ◽

Teresa Román-Berdiel ◽

...

Keyword(s):

Magnetic Susceptibility ◽

Flow Direction ◽

Anisotropy Of Magnetic Susceptibility ◽

Lava Flows ◽

Magnetic Fabric ◽

Magnetic Mineralogy ◽

Thin Sections ◽

Andesitic Lava ◽

Magnetic Fabrics ◽

Standard Specimens

The aim of this work is to apply the anisotropy of magnetic susceptibility (AMS) to determine the primary and tectonic fabrics of lava flows and volcanoclastic materials in one of the Pyrenean Stephano-Permian basins.The Pyrenean Range is a double vergence orogen located at the northern end of the Iberian Peninsula. During Carboniferous-Early Permian times the extensional or transtensional regime dominant during the progressive dismantling of the Variscan belt resulted in the development of E-W elongated intra-mountainous basins. This process was coeval with an exceptional episode of magmatic activity, both intrusive and extrusive. The Cad&#237; basin represents a good example of these structures were Stephano-Permian rocks are aligned along an E-W continuous outcrop and reach thickness of several hundreds of meters. The stratigraphy of the study area is characterized by fluviolacustrine sediments changing laterally to volcanoclastic and pyroclastic rocks with interbedded andesitic lava flows. &#160;A total of 75 sites (733 standard specimens) were studied and analysed throughout the volcanoclastic, volcanic and intrusive materials of the Stephano-Permian outcrops in the Cad&#237; basin. Samples were drilled in the field along 5 sections with N-S or NW-SE direction in the Grey and Transition Unit. Afterwards, standard specimens were measured in a Kappabridge KLY-3 (AGICO) at the Zaragoza University to characterise the magnetic fabric. The susceptibility bridge combined with a CS-3 furnace (AGICO) was used for the temperature-dependent magnetic susceptibility curves (from 20 to 700 &#176;C) to recognize the magnetic mineralogy. In addition, textural and mineralogical recognition in thin-sections of the samples was carried out in order to recognize the relationship between magnetic and petrographic fabrics.The results shows that the bulk magnetic susceptibility of the specimens ranges between 118 and 9060&#183;10-6 SI but most of the values are bracketed between 160 to 450&#183;10-6 SI. Taking into account magnetic parameters (Km, Pj and T) there is no correlation between magnetic fabrics and magnetic mineralogy and there is a dominance of triaxial and prolate ellipsoids. Thermomagnetic curves indicate the dominance of paramagnetic behaviour in all the samples and except in one case there is a ferromagnetic contribution due to the generalised presence of magnetite.Magnetic ellipsoids can be divided into four main types depending on the orientation of the main axes and associated with the lithologic types: 1) Kmax vertical and Kint and Kmin horizontal for small intrusive bodies (no restoring); 2) Kmax horizontal or subhorizontal and Kint and Kmin included in a subvertical plane (before and after restitution) for volcanic breccias; 3) Kmin vertical (after restoring) and three directional maxima for lava flows and 4) non-defined fabric for the explosive materials (probably due to their complex depositional mechanisms). In general, a dominant E-W magnetic lineation is observed in many sites, resulting either from dominant flow direction, or to secondary processes. This is the case for some of the magnetic ellipsoids, that seems to be affected by deformation, Kmin is not normal to bedding and therefore, they do not become vertical after bedding restitution.

Download Full-text