Petrogenesis of Na-rich paralava formed by methane flares associated with mud volcanism, Altyn-Emel National Park, Kazakhstan

作者：Grapes Rodney^*; Sokol Ella; Kokh Svetlana; Kozmenko Olga; Fishman Ilia

来源：Contributions to Mineralogy and Petrology, 2013, 165(4): 781-803.

DOI：10.1007/s00410-012-0835-4

• Na-rich paralava
• Combustion metamorphism
• Methane fires
• Altyn-Emel mud volcano field
• Kazakhstan

High-Na slag-like rocks (paralava) with 4.5-11 % Na2O from the Altyn-Emel mud volcanic field, Kazakhstan, are the products of melting of sediment + salt mixtures by methane flares associated with mud extrusion. The main minerals of the paralavas are diopside and wollastonite which have quench morphologies. Other high-temperature phases (crystallizing from melt and vapour phase) are tridymite, cristobalite, chlorapatite, alkali feldspar, pyrrhotite, native iron and silicon, iron phosphides, titanite, rutile, and carbon. The paralavas lack the Na-Ca silicates devitrite and combeite, but have high-Na and Na-K glasses that have not been homogenized despite low viscosities of %26lt; 10(-3.5) Pa s. The large number of ignition foci in the Altyn-Emel mud volcano field indicates gas venting from small, shallow reservoirs. The methane flares are inferred to have been small and the fire events short-lived. Fires were extinguished once overpressure released during eruption, methane venting stopped and melted rocks rapidly quenched. The periodicity of eruptions and methane flaring most likely depends on the recurrence of earthquakes (M %26lt; 5) which are frequent in this tectonically active area.

• 出版日期2013-4