Mineralogy and Origin of Fayalite–Sekaninaite Paralava: Ravat Coal Fire, Central Tajikistan

Sharygin, Victor V.; Sokol, Ellina V.; Belakovsky, Dmitriy I.

doi:10.1016/b978-0-444-59509-6.00022-3

Cited by 2 publications

(4 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Using this method, an equilibrium liquidus occurs at 1141 o C. Considering both methods we estimate the liquidus temperature to lie between 1140-and 1200 o C but much closer to 1200 o C indicated by the presence of fayalite. These estimates are similar to that suggested by Sharygin et al (2014) for the Ravat coal fire in Tajikistan where sekaninaite and fayalite also occur. This range represents the minimum high temperature reached by the Mystic Creek coal fire.…”

Section: Temperature and Pressuresupporting

confidence: 88%

“…Sekaninaite is a rare mineral but is diagnostic in very high temperature pyrometamorphic rocks and is typically associated with tridymite, olivine, orthopyroxene, mullite, Fe-Ti oxides and occasionally cristobalite, feldspar, clinopyroxene and corundum. (Grapes et al, 2011;Sharygin, et al, 2014) OM1).…”

Section: Mineral Chemistrymentioning

confidence: 99%

“…Sen, 1957;Wahrhaftig et al, 1969;Foit et al, 1987;Cosca et al, 1989;Sharygin et al, 1999Sharygin et al, , 2009Sharygin et al, , 2014Grapes, 2011;Grapes et al 2009Grapes et al , 2011Thiéry et al, 2018,;Guy et al 2020). There is abundant evidence for fires that have since burned out and others that have burned for decades and even thousands of years (Sharygin et al, 2014). In this study we investigate a prehistoric coal-seam fire in the Nenana coal basin in the Alaska Range (Fig.…”

Section: Introductionmentioning

confidence: 98%

“…Coal-seam fires have occurred world-wide throughout geologic time (e.g. Sen, 1957;Wahrhaftig et al, 1969;Foit et al, 1987;Cosca et al, 1989;Sharygin et al, 1999Sharygin et al, , 2009Sharygin et al, , 2014Grapes, 2011;Grapes et al 2009Grapes et al , 2011Thiéry et al, 2018,;Guy et al 2020). There is abundant evidence for fires that have since burned out and others that have burned for decades and even thousands of years (Sharygin et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A rare sekaninaite occurrence in the Nenana Coal Basin, Alaska Range, Alaska

Reidel,

Ross

2023

American Mineralogist

View full text Add to dashboard Cite

Coal-seam fires are not uncommon and occur in coal deposits of all ages. Coal-seam fires have been noted in Alaska, but this paper is the first to describe the mineralogy and petrology of a This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

show abstract

Section: Temperature and Pressuresupporting

confidence: 88%

Section: Mineral Chemistrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A rare sekaninaite occurrence in the Nenana Coal Basin, Alaska Range, Alaska

Reidel,

Ross

2023

American Mineralogist

View full text Add to dashboard Cite

show abstract

Pyrometamorphic Rocks in the Molinicos Basin (Betic Cordillera, SE Spain): Insights into the Generation of Cordierite Paralavas

et al. 2019

View full text Add to dashboard Cite

A singular thermal anomaly occurred in the Molinicos Miocene, lacustrine, intramontane basin (Betic Cordillera). This gave place to vitreous vesicular materials (paralavas) and baked rocks (clinker) inside of a sequence of marly diatomites and limestones. The chemical composition of the paralavas (SiO 2 = 52-57, Al 2 O 3 ≈ 20, Fe 2 O 3 = 10-20, K 2 O + Na 2 O < 2.5, CaO < 4.5, and MgO < 1.5, % in weight), which is very different from typical igneous rocks, and their high-T mineralogy (cordierite, sillimanite, anorthite, mullite, and high-T silica polymorphs) suggest that they formed during a pyrometamorphic event. The occurrence of dry intervals in the lacustrine depositional system, the high Total Organic Carbon contents (>4% in weight) of dark clay layers and the existence of tectonic fractures give the right context for a combustion process. Short-term heating favoured the generation of paralavas, clinker and marbles. Thermodynamic modelling constrains the onset of melting at 870-920 • C for <10 MPa at equilibrium conditions. However, the presence of tridymite and/or cristobalite in clinker and paralavas and the compositional variation in both rock types suggests that the temperature at which first melting occurred ranged between 870 • C and 1260 • C due to melt fractionation processes.Minerals 2019, 9, 748 2 of 24 evacuation of combustion products [22]. At the same time, thermal isolation is necessary to accumulate locally enough heat until an activation threshold is reached [29]. Thus, depth and extension of the fires are commonly restricted to some tens of square metres, limited in addition by the position of the water table. However, much larger areas have been described reaching hundreds of square kilometres [22].During combustion metamorphism, the sedimentary rocks around the ignition foci are subjected to certain changes in addition to common dehydration, and decarbonation in case CaCO 3 is present. Firstly, the rocks are hardened and, later, they become sintered and recrystallised producing a ceramic texture. The colour of the rocks is also progressively changed from yellow to more intense orange and red, due to iron oxidation, and finally even grey and black when reducing conditions are reached. In any case, this intense thermal metamorphism triggers only limited fusion of the sediments. The released melts may flow along fractures but usually undergo fast cooling producing small amounts of glass with particular mineral assemblages and textures similar to those of fine-grained volcanic rocks. These rocks, which show features and parageneses merging with those of igneous rocks, are called paralavas and the associated baked or partially melted sedimentary rocks are denominated clinker e.g., [24,[31][32][33][34]. According to Cosca and Essene [35] the mineral assemblages produced in paralavas are partly a function of the temperature, degree of partial melting, and oxidation state related to local gas buffers, in addition to the original bulk composition of the sedimentary protolith. Fast heating and subs...

show abstract

Mineralogy and Origin of Fayalite–Sekaninaite Paralava: Ravat Coal Fire, Central Tajikistan

Cited by 2 publications

References 23 publications

A rare sekaninaite occurrence in the Nenana Coal Basin, Alaska Range, Alaska

A rare sekaninaite occurrence in the Nenana Coal Basin, Alaska Range, Alaska

Pyrometamorphic Rocks in the Molinicos Basin (Betic Cordillera, SE Spain): Insights into the Generation of Cordierite Paralavas

Contact Info

Product

Resources

About