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T B Nimalsiri - One of the best experts on this subject based on the ideXlab platform.
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p t evolution of a spinel quartz bearing khondalite from the highland complex sri lanka implications for non uht metamorphism
Journal of Asian Earth Sciences, 2014Co-Authors: P L Dharmapriya, Sanjeewa P K Malaviarachchi, Andrea Galli, Benxun Su, N.d. Subasinghe, C.b. Dissanayake, T B NimalsiriAbstract:Abstract Here, we report a natural field example for the coexistence of spinel + quartz as a non-UHT assemblage in spinel- and cordierite-bearing garnet-Sillimanite-biotite-graphite gneiss (khondalite) interbedded with orthopyroxene-garnet-biotite bearing intermediate granulites from the Highland Complex (HC) in Sri Lanka. The khondalite contains Zn-rich spinel mainly in four textural assemblages namely: (a) spinel co-existing with tiny quartz (ZnO = 12.67–12.85 wt%), (b) spinel surrounded by Sillimanite moates and in intergrowth with skeletal Sillimanites (ZnO = 9.03–9.17 wt%), (c) symplectitic spinels at the margin of Sillimanite (ZnO = 4.09–4.28 wt%) and (d) spinel co-existing with ilmenite or as isolated grains (ZnO = 7.61–7.97 wt% and Cr 2 O 3 = 5.99–6.27 wt%). Assemblage (a) and (b) occur within garnet while assemblages of (c) and (d) are present within cordierite moates after garnet in the matrix. Pseudosections calculated in the NCKFMASHTMnO system and conventional geothermobarometry suggest that the metamorphic peak conditions attained by the spinel + quartz bearing khondalites and associated intermediate granulites did not exceed T of 900 °C and P of 7.5–8.5 kbar. Post-peak evolution was characterized by a stage of nearly-isobaric cooling down to T of 770 °C and P of 7.5 kbar, followed by a late stage of isothermal decompression down to P T of 770 °C. We propose that the incorporation of large amount of Zn into spinel from exotic, metasomatic fluids and possibly incorporation of Fe 3+ into spinel under high oxidizing conditions may have shifted the stabilization of co-existing spinel + quartz to T
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P–T evolution of a spinel + quartz bearing khondalite from the Highland Complex, Sri Lanka: Implications for non-UHT metamorphism
Journal of Asian Earth Sciences, 2014Co-Authors: P L Dharmapriya, Sanjeewa P K Malaviarachchi, Andrea Galli, Benxun Su, N.d. Subasinghe, C.b. Dissanayake, T B NimalsiriAbstract:Abstract Here, we report a natural field example for the coexistence of spinel + quartz as a non-UHT assemblage in spinel- and cordierite-bearing garnet-Sillimanite-biotite-graphite gneiss (khondalite) interbedded with orthopyroxene-garnet-biotite bearing intermediate granulites from the Highland Complex (HC) in Sri Lanka. The khondalite contains Zn-rich spinel mainly in four textural assemblages namely: (a) spinel co-existing with tiny quartz (ZnO = 12.67–12.85 wt%), (b) spinel surrounded by Sillimanite moates and in intergrowth with skeletal Sillimanites (ZnO = 9.03–9.17 wt%), (c) symplectitic spinels at the margin of Sillimanite (ZnO = 4.09–4.28 wt%) and (d) spinel co-existing with ilmenite or as isolated grains (ZnO = 7.61–7.97 wt% and Cr 2 O 3 = 5.99–6.27 wt%). Assemblage (a) and (b) occur within garnet while assemblages of (c) and (d) are present within cordierite moates after garnet in the matrix. Pseudosections calculated in the NCKFMASHTMnO system and conventional geothermobarometry suggest that the metamorphic peak conditions attained by the spinel + quartz bearing khondalites and associated intermediate granulites did not exceed T of 900 °C and P of 7.5–8.5 kbar. Post-peak evolution was characterized by a stage of nearly-isobaric cooling down to T of 770 °C and P of 7.5 kbar, followed by a late stage of isothermal decompression down to P T of 770 °C. We propose that the incorporation of large amount of Zn into spinel from exotic, metasomatic fluids and possibly incorporation of Fe 3+ into spinel under high oxidizing conditions may have shifted the stabilization of co-existing spinel + quartz to T
P L Dharmapriya - One of the best experts on this subject based on the ideXlab platform.
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p t evolution of a spinel quartz bearing khondalite from the highland complex sri lanka implications for non uht metamorphism
Journal of Asian Earth Sciences, 2014Co-Authors: P L Dharmapriya, Sanjeewa P K Malaviarachchi, Andrea Galli, Benxun Su, N.d. Subasinghe, C.b. Dissanayake, T B NimalsiriAbstract:Abstract Here, we report a natural field example for the coexistence of spinel + quartz as a non-UHT assemblage in spinel- and cordierite-bearing garnet-Sillimanite-biotite-graphite gneiss (khondalite) interbedded with orthopyroxene-garnet-biotite bearing intermediate granulites from the Highland Complex (HC) in Sri Lanka. The khondalite contains Zn-rich spinel mainly in four textural assemblages namely: (a) spinel co-existing with tiny quartz (ZnO = 12.67–12.85 wt%), (b) spinel surrounded by Sillimanite moates and in intergrowth with skeletal Sillimanites (ZnO = 9.03–9.17 wt%), (c) symplectitic spinels at the margin of Sillimanite (ZnO = 4.09–4.28 wt%) and (d) spinel co-existing with ilmenite or as isolated grains (ZnO = 7.61–7.97 wt% and Cr 2 O 3 = 5.99–6.27 wt%). Assemblage (a) and (b) occur within garnet while assemblages of (c) and (d) are present within cordierite moates after garnet in the matrix. Pseudosections calculated in the NCKFMASHTMnO system and conventional geothermobarometry suggest that the metamorphic peak conditions attained by the spinel + quartz bearing khondalites and associated intermediate granulites did not exceed T of 900 °C and P of 7.5–8.5 kbar. Post-peak evolution was characterized by a stage of nearly-isobaric cooling down to T of 770 °C and P of 7.5 kbar, followed by a late stage of isothermal decompression down to P T of 770 °C. We propose that the incorporation of large amount of Zn into spinel from exotic, metasomatic fluids and possibly incorporation of Fe 3+ into spinel under high oxidizing conditions may have shifted the stabilization of co-existing spinel + quartz to T
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P–T evolution of a spinel + quartz bearing khondalite from the Highland Complex, Sri Lanka: Implications for non-UHT metamorphism
Journal of Asian Earth Sciences, 2014Co-Authors: P L Dharmapriya, Sanjeewa P K Malaviarachchi, Andrea Galli, Benxun Su, N.d. Subasinghe, C.b. Dissanayake, T B NimalsiriAbstract:Abstract Here, we report a natural field example for the coexistence of spinel + quartz as a non-UHT assemblage in spinel- and cordierite-bearing garnet-Sillimanite-biotite-graphite gneiss (khondalite) interbedded with orthopyroxene-garnet-biotite bearing intermediate granulites from the Highland Complex (HC) in Sri Lanka. The khondalite contains Zn-rich spinel mainly in four textural assemblages namely: (a) spinel co-existing with tiny quartz (ZnO = 12.67–12.85 wt%), (b) spinel surrounded by Sillimanite moates and in intergrowth with skeletal Sillimanites (ZnO = 9.03–9.17 wt%), (c) symplectitic spinels at the margin of Sillimanite (ZnO = 4.09–4.28 wt%) and (d) spinel co-existing with ilmenite or as isolated grains (ZnO = 7.61–7.97 wt% and Cr 2 O 3 = 5.99–6.27 wt%). Assemblage (a) and (b) occur within garnet while assemblages of (c) and (d) are present within cordierite moates after garnet in the matrix. Pseudosections calculated in the NCKFMASHTMnO system and conventional geothermobarometry suggest that the metamorphic peak conditions attained by the spinel + quartz bearing khondalites and associated intermediate granulites did not exceed T of 900 °C and P of 7.5–8.5 kbar. Post-peak evolution was characterized by a stage of nearly-isobaric cooling down to T of 770 °C and P of 7.5 kbar, followed by a late stage of isothermal decompression down to P T of 770 °C. We propose that the incorporation of large amount of Zn into spinel from exotic, metasomatic fluids and possibly incorporation of Fe 3+ into spinel under high oxidizing conditions may have shifted the stabilization of co-existing spinel + quartz to T
Lutz Nasdala - One of the best experts on this subject based on the ideXlab platform.
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Shock-induced formation of kyanite (Al_2SiO_5) from Sillimanite within a dense metamorphic rock from the Ries crater (Germany)
Contributions to Mineralogy and Petrology, 2004Co-Authors: Volker Stähle, Mario Koch, Rainer Altherr, Lutz NasdalaAbstract:A dense (ρ~3.34 g cm^−3) garnet–Sillimanite-rich metamorphic rock from the suevite breccia of the Ries impact crater was studied by scanning-electron microscopy and Raman microprobe spectroscopy. In the strongly shocked rock clast kyanite was formed from Sillimanite under momentary high pressures of natural shock waves. Kyanite aggregates were found as thin (~0.3–2.0 μm) seams along grain boundaries between, and fractures within, Sillimanite grains. Within these seams kyanite c -axes are oriented perpendicular to original grain boundaries and fractures. In addition, larger (up to 10 μm) isolated kyanite grains were rarely found within host Sillimanite. Filamentary kyanite aggregates and isolated crystals typically show shrinkage cracks due to volume decrease (~10%). Locally, broad interstices between Sillimanite crystals are filled with aluminosilicate glass containing a high volume fraction of sub-micrometer-sized euhedral crystals. The silica-rich glass suggests incongruent melting of Sillimanite at local post-shock temperatures significantly higher than 1,300°C. The edges of adjacent Sillimanite grains are thermally and chemically altered. The local generation of temperature spikes is attributed to strong shock wave interactions due to very high shock impedance contrasts.
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shock induced formation of kyanite al2sio5 from Sillimanite within a dense metamorphic rock from the ries crater germany
Contributions to Mineralogy and Petrology, 2004Co-Authors: Volker Stähle, Mario Koch, Rainer Altherr, Lutz NasdalaAbstract:A dense (ρ~3.34 g cm−3) garnet–Sillimanite-rich metamorphic rock from the suevite breccia of the Ries impact crater was studied by scanning-electron microscopy and Raman microprobe spectroscopy. In the strongly shocked rock clast kyanite was formed from Sillimanite under momentary high pressures of natural shock waves. Kyanite aggregates were found as thin (~0.3–2.0 μm) seams along grain boundaries between, and fractures within, Sillimanite grains. Within these seams kyanite c-axes are oriented perpendicular to original grain boundaries and fractures. In addition, larger (up to 10 μm) isolated kyanite grains were rarely found within host Sillimanite. Filamentary kyanite aggregates and isolated crystals typically show shrinkage cracks due to volume decrease (~10%). Locally, broad interstices between Sillimanite crystals are filled with aluminosilicate glass containing a high volume fraction of sub-micrometer-sized euhedral crystals. The silica-rich glass suggests incongruent melting of Sillimanite at local post-shock temperatures significantly higher than 1,300°C. The edges of adjacent Sillimanite grains are thermally and chemically altered. The local generation of temperature spikes is attributed to strong shock wave interactions due to very high shock impedance contrasts.
C.b. Dissanayake - One of the best experts on this subject based on the ideXlab platform.
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p t evolution of a spinel quartz bearing khondalite from the highland complex sri lanka implications for non uht metamorphism
Journal of Asian Earth Sciences, 2014Co-Authors: P L Dharmapriya, Sanjeewa P K Malaviarachchi, Andrea Galli, Benxun Su, N.d. Subasinghe, C.b. Dissanayake, T B NimalsiriAbstract:Abstract Here, we report a natural field example for the coexistence of spinel + quartz as a non-UHT assemblage in spinel- and cordierite-bearing garnet-Sillimanite-biotite-graphite gneiss (khondalite) interbedded with orthopyroxene-garnet-biotite bearing intermediate granulites from the Highland Complex (HC) in Sri Lanka. The khondalite contains Zn-rich spinel mainly in four textural assemblages namely: (a) spinel co-existing with tiny quartz (ZnO = 12.67–12.85 wt%), (b) spinel surrounded by Sillimanite moates and in intergrowth with skeletal Sillimanites (ZnO = 9.03–9.17 wt%), (c) symplectitic spinels at the margin of Sillimanite (ZnO = 4.09–4.28 wt%) and (d) spinel co-existing with ilmenite or as isolated grains (ZnO = 7.61–7.97 wt% and Cr 2 O 3 = 5.99–6.27 wt%). Assemblage (a) and (b) occur within garnet while assemblages of (c) and (d) are present within cordierite moates after garnet in the matrix. Pseudosections calculated in the NCKFMASHTMnO system and conventional geothermobarometry suggest that the metamorphic peak conditions attained by the spinel + quartz bearing khondalites and associated intermediate granulites did not exceed T of 900 °C and P of 7.5–8.5 kbar. Post-peak evolution was characterized by a stage of nearly-isobaric cooling down to T of 770 °C and P of 7.5 kbar, followed by a late stage of isothermal decompression down to P T of 770 °C. We propose that the incorporation of large amount of Zn into spinel from exotic, metasomatic fluids and possibly incorporation of Fe 3+ into spinel under high oxidizing conditions may have shifted the stabilization of co-existing spinel + quartz to T
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P–T evolution of a spinel + quartz bearing khondalite from the Highland Complex, Sri Lanka: Implications for non-UHT metamorphism
Journal of Asian Earth Sciences, 2014Co-Authors: P L Dharmapriya, Sanjeewa P K Malaviarachchi, Andrea Galli, Benxun Su, N.d. Subasinghe, C.b. Dissanayake, T B NimalsiriAbstract:Abstract Here, we report a natural field example for the coexistence of spinel + quartz as a non-UHT assemblage in spinel- and cordierite-bearing garnet-Sillimanite-biotite-graphite gneiss (khondalite) interbedded with orthopyroxene-garnet-biotite bearing intermediate granulites from the Highland Complex (HC) in Sri Lanka. The khondalite contains Zn-rich spinel mainly in four textural assemblages namely: (a) spinel co-existing with tiny quartz (ZnO = 12.67–12.85 wt%), (b) spinel surrounded by Sillimanite moates and in intergrowth with skeletal Sillimanites (ZnO = 9.03–9.17 wt%), (c) symplectitic spinels at the margin of Sillimanite (ZnO = 4.09–4.28 wt%) and (d) spinel co-existing with ilmenite or as isolated grains (ZnO = 7.61–7.97 wt% and Cr 2 O 3 = 5.99–6.27 wt%). Assemblage (a) and (b) occur within garnet while assemblages of (c) and (d) are present within cordierite moates after garnet in the matrix. Pseudosections calculated in the NCKFMASHTMnO system and conventional geothermobarometry suggest that the metamorphic peak conditions attained by the spinel + quartz bearing khondalites and associated intermediate granulites did not exceed T of 900 °C and P of 7.5–8.5 kbar. Post-peak evolution was characterized by a stage of nearly-isobaric cooling down to T of 770 °C and P of 7.5 kbar, followed by a late stage of isothermal decompression down to P T of 770 °C. We propose that the incorporation of large amount of Zn into spinel from exotic, metasomatic fluids and possibly incorporation of Fe 3+ into spinel under high oxidizing conditions may have shifted the stabilization of co-existing spinel + quartz to T
Andrea Galli - One of the best experts on this subject based on the ideXlab platform.
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p t evolution of a spinel quartz bearing khondalite from the highland complex sri lanka implications for non uht metamorphism
Journal of Asian Earth Sciences, 2014Co-Authors: P L Dharmapriya, Sanjeewa P K Malaviarachchi, Andrea Galli, Benxun Su, N.d. Subasinghe, C.b. Dissanayake, T B NimalsiriAbstract:Abstract Here, we report a natural field example for the coexistence of spinel + quartz as a non-UHT assemblage in spinel- and cordierite-bearing garnet-Sillimanite-biotite-graphite gneiss (khondalite) interbedded with orthopyroxene-garnet-biotite bearing intermediate granulites from the Highland Complex (HC) in Sri Lanka. The khondalite contains Zn-rich spinel mainly in four textural assemblages namely: (a) spinel co-existing with tiny quartz (ZnO = 12.67–12.85 wt%), (b) spinel surrounded by Sillimanite moates and in intergrowth with skeletal Sillimanites (ZnO = 9.03–9.17 wt%), (c) symplectitic spinels at the margin of Sillimanite (ZnO = 4.09–4.28 wt%) and (d) spinel co-existing with ilmenite or as isolated grains (ZnO = 7.61–7.97 wt% and Cr 2 O 3 = 5.99–6.27 wt%). Assemblage (a) and (b) occur within garnet while assemblages of (c) and (d) are present within cordierite moates after garnet in the matrix. Pseudosections calculated in the NCKFMASHTMnO system and conventional geothermobarometry suggest that the metamorphic peak conditions attained by the spinel + quartz bearing khondalites and associated intermediate granulites did not exceed T of 900 °C and P of 7.5–8.5 kbar. Post-peak evolution was characterized by a stage of nearly-isobaric cooling down to T of 770 °C and P of 7.5 kbar, followed by a late stage of isothermal decompression down to P T of 770 °C. We propose that the incorporation of large amount of Zn into spinel from exotic, metasomatic fluids and possibly incorporation of Fe 3+ into spinel under high oxidizing conditions may have shifted the stabilization of co-existing spinel + quartz to T
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P–T evolution of a spinel + quartz bearing khondalite from the Highland Complex, Sri Lanka: Implications for non-UHT metamorphism
Journal of Asian Earth Sciences, 2014Co-Authors: P L Dharmapriya, Sanjeewa P K Malaviarachchi, Andrea Galli, Benxun Su, N.d. Subasinghe, C.b. Dissanayake, T B NimalsiriAbstract:Abstract Here, we report a natural field example for the coexistence of spinel + quartz as a non-UHT assemblage in spinel- and cordierite-bearing garnet-Sillimanite-biotite-graphite gneiss (khondalite) interbedded with orthopyroxene-garnet-biotite bearing intermediate granulites from the Highland Complex (HC) in Sri Lanka. The khondalite contains Zn-rich spinel mainly in four textural assemblages namely: (a) spinel co-existing with tiny quartz (ZnO = 12.67–12.85 wt%), (b) spinel surrounded by Sillimanite moates and in intergrowth with skeletal Sillimanites (ZnO = 9.03–9.17 wt%), (c) symplectitic spinels at the margin of Sillimanite (ZnO = 4.09–4.28 wt%) and (d) spinel co-existing with ilmenite or as isolated grains (ZnO = 7.61–7.97 wt% and Cr 2 O 3 = 5.99–6.27 wt%). Assemblage (a) and (b) occur within garnet while assemblages of (c) and (d) are present within cordierite moates after garnet in the matrix. Pseudosections calculated in the NCKFMASHTMnO system and conventional geothermobarometry suggest that the metamorphic peak conditions attained by the spinel + quartz bearing khondalites and associated intermediate granulites did not exceed T of 900 °C and P of 7.5–8.5 kbar. Post-peak evolution was characterized by a stage of nearly-isobaric cooling down to T of 770 °C and P of 7.5 kbar, followed by a late stage of isothermal decompression down to P T of 770 °C. We propose that the incorporation of large amount of Zn into spinel from exotic, metasomatic fluids and possibly incorporation of Fe 3+ into spinel under high oxidizing conditions may have shifted the stabilization of co-existing spinel + quartz to T
