Feldspar crystallization and the behavior of fluorine in the Utagi trachyte, Oki-Dogo, Japan

Nakano, Satoshi; Makino, Kuniaki

doi:10.1016/j.lithos.2022.106676

Cited by 2 publications

(2 citation statements)

References 47 publications

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“…The fluorite alignments are characteristically braided. The braided occurrence of fluorite alignments in TST feldspars quite differs from non-braided alignments along the Murchison and a-axis directions developed in UTT feldspars (Nakano and Makino, 2022), but similar to that in the HET feldspars (Nakano and Makino, 2024).…”

Section: A C C E P T E D I N J M P S P R E -P R O O Fmentioning

confidence: 80%

“…Feldspar microtextures record a variety of information about various geological, petrological, and mineralogical processes (e.g., Deer et al, 2001). The analyses of them in alkaline volcanic rocks from Oki-Dogo Island, Sea of Japan, have added new information on solidification processes of dry (relatively or practically anhydrous) alkaline magmas: the examined rocks are hypersthene-augite trachyte (lava) (Nakano, 1992), alkali rhyolite (lava) (Nakano and Suwa, 1995), ferro-augite trachyte (FAT; lava) (Nakano, 2021), olivine-hedenbergite trachyte from Utagi (UTT; sheet) (Nakano and Makino, 2022), and sanidine trachyte from Hei (HET; sheet) (Nakano and Makino, 2024). Complex internal microtextures comprising lamellar, wavy, patchy, and domain textures in feldspars have been observed with or without anti-rapakivi core-mantle zoning in the individual rocks.…”

Section: Introductionmentioning

confidence: 99%

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Fluorite alignments cutting metasomatic textures in trachyte feldspars from Oki-Dogo Island, Sea of Japan

NAKANO

2024

Journal of Mineralogical and Petrological Sciences

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Feldspar internal textures in a pyroclastic trachyte from Oki-Dogo, Sea of Japan, were examined to expand the understanding of feldspar reactions during the cooling through magmatic to hydrothermal stages, beyond the previous information of feldspars in Oki-Dogo alkaline lava and sheet rocks, using the methods of an electron microprobe and cathodoluminescence. Two types of micron-size internal microtextures were found to coexist in individual feldspar phenocrysts: clear domain textures, formed during a high-temperature magmatic stage, and turbid microperthitic textures, formed during a low-temperature subsolidus stage. The both microtextures are products of metasomatic replacement reactions. In addition, nano-size fluorite grains are aligned across the microtextures. The fluorite occurrence records the behavior of fluorine related to feldspar reactions.

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Section: A C C E P T E D I N J M P S P R E -P R O O Fmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Fluorite alignments cutting metasomatic textures in trachyte feldspars from Oki-Dogo Island, Sea of Japan

NAKANO

2024

Journal of Mineralogical and Petrological Sciences

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Magmatic processes forming replacement textures with fluorite alignments in feldspars in an evolved trachyte from Oki‐Dogo Island, Sea of Japan

Nakano,

Makino

2024

Island Arc

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Internal microtextures of ternary alkali feldspars in sanidine trachyte from Oki‐Dogo Island were examined using an electron microprobe analyzer, a scanning electron microscope, a transmission electron microscope and cathodoluminescence instruments, to develop the understanding of volcanic processes of alkaline magmas related to feldspar crystallization. The examined trachyte is an evolved rock of the Oki‐Dogo Pliocene trachyte group. Its phenocryst feldspars are commonly associated with lamellar‐wavy‐domain textures with scales approximately from 100 nm up to several hundreds of μm that show complex and gradual variations in composition: however, anti‐rapakivi zoning textures common in other Oki‐Dogo alkaline rocks are almost completely absent in the trachyte. These textures are produced by extensive magmatic ion‐exchange replacement reactions progressively advanced in the evolved magma. Characteristic braided fluorite alignments are developed consistently with lamellar‐wavy‐domain textures in phenocryst feldspars, and similar braided alignments are also present in groundmass feldspars with complicated microtextures. Most of fluorite grains are <100 nm in diameter, and the patterns of braided fluorite alignments vary greatly in individual feldspars. The whole occurrence of the feldspar microtextures represents an extreme example of diffusion‐controlled replacement reactions, progressively advanced in the dry (relatively anhydrous) trachyte magma. The genetic processes forming fluorite alignments in feldspars are related to magma compositions, especially F and P contents, and the crystallization of F‐bearing minerals, especially of fluorapatite.

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Feldspar crystallization and the behavior of fluorine in the Utagi trachyte, Oki-Dogo, Japan

Cited by 2 publications

References 47 publications

Fluorite alignments cutting metasomatic textures in trachyte feldspars from Oki-Dogo Island, Sea of Japan

Fluorite alignments cutting metasomatic textures in trachyte feldspars from Oki-Dogo Island, Sea of Japan

Magmatic processes forming replacement textures with fluorite alignments in feldspars in an evolved trachyte from Oki‐Dogo Island, Sea of Japan

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