- #151
- 7,747
- 3,965
Next sample:
Tinguaite. Altered phonolite (QAPF field 11), Fen complex. Trachytic groundmass of sanidine laths, aegerine needles, and small aggregates of anhedral granular mineral, likely muscovite/paragonite secondary to groundmass nepheline.
Small phenocrysts of biotite, large phenocrysts of sanidine, often partially altered into natrolite and large blocky phenocrysts of what was likely nepheline, now pseudomorphically altered into disordered microscopic anhedral aggregations of presumably the same mineral (biotite or paragonite) as the groundmass as well as the altered nepheline found in samples Fen 248, 249, and 250; unfortunately, definitive identification is not possible.
AI coughed up the following- keep in mind that the pre-existing country rock, Telemark gniess, has significantly less Aluminum and significantly more Sodium compared to the rest of the rocks on earth, so the gneiss is classified as “peralkaline”. Within the Fen complex, due to the ijolite/carbonatite intrusions, the Fen rocks are usually classified as “silica-undersaturated peralkaline”.
“The alteration of sanidine into natrolite is a hydrothermal process, typically occurring within silica-undersaturated volcanic rocks like phonolites or nepheline syenites. While sanidine itself is a high-temperature potassium-sodium feldspar, its alteration to natrolite—a hydrated sodium-aluminum silicate zeolite—represents a low-temperature, secondary, or "deuteric" alteration event.”
Tinguaite. Altered phonolite (QAPF field 11), Fen complex. Trachytic groundmass of sanidine laths, aegerine needles, and small aggregates of anhedral granular mineral, likely muscovite/paragonite secondary to groundmass nepheline.
Small phenocrysts of biotite, large phenocrysts of sanidine, often partially altered into natrolite and large blocky phenocrysts of what was likely nepheline, now pseudomorphically altered into disordered microscopic anhedral aggregations of presumably the same mineral (biotite or paragonite) as the groundmass as well as the altered nepheline found in samples Fen 248, 249, and 250; unfortunately, definitive identification is not possible.
AI coughed up the following- keep in mind that the pre-existing country rock, Telemark gniess, has significantly less Aluminum and significantly more Sodium compared to the rest of the rocks on earth, so the gneiss is classified as “peralkaline”. Within the Fen complex, due to the ijolite/carbonatite intrusions, the Fen rocks are usually classified as “silica-undersaturated peralkaline”.
“The alteration of sanidine into natrolite is a hydrothermal process, typically occurring within silica-undersaturated volcanic rocks like phonolites or nepheline syenites. While sanidine itself is a high-temperature potassium-sodium feldspar, its alteration to natrolite—a hydrated sodium-aluminum silicate zeolite—represents a low-temperature, secondary, or "deuteric" alteration event.”