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Polozov A.G.,RAS Institute of Geology and Mineralogy | Svensen H.H.,Center for Earth Evolution and Dynamics | Planke S.,Center for Earth Evolution and Dynamics | Planke S.,Volcanic Basin Petroleum Research AS VBPR | And 5 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2016

A number of mechanisms have been proposed to explain the end-Permian crisis. Many of them explore the link between this catastrophe and the Siberian Traps. We test the hypothesis that eruption of thermogenic gas generated in contact aureoles around igneous sills intruded into evaporite sequences of the Tunguska Basin triggered the crisis. In particular, we test the idea that the aspect that breccia pipes represent conduits for voluminous gas migration from the deep basins to the atmosphere. This contribution sheds new light on the pipe formation based on new field and borehole observations and electron microscopy analyses. Of more than three hundred mapped magnetite-bearing basalt pipes, 43 are classified as diatremes. The diatremes are usually circular or elliptical, with multiple zones of brecciation reaching the surface, sometimes with preserved in-filled crater lakes. The pipe diameter on the surface varies from a few tens of meters for small single diatremes to about a kilometer. The largest crater lake area is 2.7km2. We have conducted a detailed study of the breccias in the Sholokhovsk basalt pipe located within the Nepa potash deposit in the Tunguska Basin, Siberia, Russia (about N 59° and E 107°) and find that the breccias are cemented by carbonate matrix (calcite, dolomite) and halite. Breccia clasts are altered at various temperatures, evidenced by growth of albite and garnet from basaltic glass, and diopside, garnet, magnetite and chlorine-bearing amphibole (up to 1.8% Cl) in altered magmatic clasts. These mineral assemblages suggest high temperature interactions with evaporites within the pipe conduits. The large number of pipes support that degassing of halogen-rich volatiles was a widespread and violent process with implications for the end-Permian crisis. © 2015 Elsevier B.V. Source


Polozov A.G.,RAS Institute of Geology and Mineralogy | Polozov A.G.,Center for Earth Evolution and Dynamics | Svensen H.H.,Center for Earth Evolution and Dynamics | Planke S.,Center for Earth Evolution and Dynamics | And 5 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2015

A number of mechanisms have been proposed to explain the end-Permian crisis. Many of them explore the link between this catastrophe and the Siberian Traps. We test the hypothesis that eruption of thermogenic gas generated in contact aureoles around igneous sills intruded into evaporite sequences of the Tunguska Basin triggered the crisis. In particular, we test the idea that the aspect that breccia pipes represent conduits for voluminous gas migration from the deep basins to the atmosphere. This contribution sheds new light on the pipe formation based on new field and borehole observations and electron microscopy analyses. Of more than three hundred mapped magnetite-bearing basalt pipes, 43 are classified as diatremes. The diatremes are usually circular or elliptical, with multiple zones of brecciation reaching the surface, sometimes with preserved in-filled crater lakes. The pipe diameter on the surface varies from a few tens of meters for small single diatremes to about a kilometer. The largest crater lake area is 2.7km2. We have conducted a detailed study of the breccias in the Sholokhovsk basalt pipe located within the Nepa potash deposit in the Tunguska Basin, Siberia, Russia (about N 59° and E 107°) and find that the breccias are cemented by carbonate matrix (calcite, dolomite) and halite. Breccia clasts are altered at various temperatures, evidenced by growth of albite and garnet from basaltic glass, and diopside, garnet, magnetite and chlorine-bearing amphibole (up to 1.8% Cl) in altered magmatic clasts. These mineral assemblages suggest high temperature interactions with evaporites within the pipe conduits. The large number of pipes support that degassing of halogen-rich volatiles was a widespread and violent process with implications for the end-Permian crisis. © 2015 Elsevier B.V. Source


Senger K.,University of Bergen | Senger K.,University Center in Svalbard | Tveranger J.,University of Bergen | Ogata K.,University Center in Svalbard | And 5 more authors.
Earth-Science Reviews | Year: 2014

Late Mesozoic mafic igneous rocks are widespread across the Arctic region, and are collectively referred to as the High Arctic Large Igneous Province (HALIP). In Svalbard the HALIP is represented by the Diabasodden Suite, an extensive system of predominantly basic intrusive doleritic rocks. Associated lava flows are exposed on the far east of the archipelago. Two main igneous centres have been proposed: (1) Central Spitsbergen and (2) the eastern Svalbard dolerite belt, spanning Hinlopenstretet and the islands of Edgeøya and Barentsøya. Offshore seismic and magnetic data suggest a link between the Svalbard and Franz Joseph Land igneous exposures. Intrusions occur predominantly as sills, up to 100. m thick and laterally continuous for up to 30 km. Dykes are present locally, and range in thickness from < 10 m up to 100 m. A compilation of published geochemical data reveals that the vast majority of samples have a basaltic geochemical signature. Comparison to HALIP rocks elsewhere in the Arctic, including paleotectonic reconstructions, suggests that the Diabasodden Suite formed as part of an intra-plate basaltic complex originating from a source near the Alpha Ridge. Apart from Late Mesozoic magmatism, Svalbard has also experienced magmatic activity both before and after the intrusion of the Diabasodden Suite dolerites. These are distinguished on the basis of their geochemical signature and timing. Timing of the Diabasodden Suite magmatism is currently poorly constrained. More than 130 radiometric (Ar-Ar and K-Ar) ages have been published, with a wide range of ages (ca. 75-145 Ma). Modern radiometric dating (U-Pb) on three samples suggests a shorter-lived intrusion pulse at ca. 124.5 Ma (i.e. early Aptian). While much work has been conducted on the Diabasodden Suite in the past, a detailed synthesis of this widespread unit is presently missing. In this contribution we discuss the current knowledge on the Diabasodden Suite, synthesizing and reviewing the past studies as well as pointing out possible future research directions. © 2014 Elsevier B.V. Source

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