The Mount Genis granite is one of the post-tectonic intrusives emplaced late in the magmatic history of the Hercynian batholith in Sardinia. Devitrified silicate melt inclusion are present in some (magmatic) rock-forming and miarolitic quartz. These magmatic remnants show initial melting at 680-720-degrees-C. High-temperature observations (700-800-degrees-C) revealed the presence in some of the inclusions of mixed hydrosaline melt (Li) and silicate melt (L2), with extremely variable L1/L2 ratios. Electron microprobe analyses indicate LI to be K-Na dominated chlorides. Inclusions of mixed silicate and hydrosaline melts are interpreted to have been formed by heterogeneous trapping of two immiscible fluid phases (silicate-hydrosaline) after second boiling, most likely during the final crystallization stage. Magma-derived brines (63 eq wt% NaCl) circulated at subsolidus conditions from almost-equal-to 600-degrees-C and were retained in the miarolitic cavities down to about 400-degrees-C. Fluid unmixing occurred locally in the miarolitic cavities from 550-degrees to 412-degrees-C. At temperatures of almost-equal-to 400-degrees to 100-degrees-C the microgranite was invaded by diluted waters (almost-equal-to 4-5 cq wt% NaCl). A possible model for fluid evolution begins with a hydrosaline melt exsolving from the magma at the late-magmatic stage. The absence of boiling within the volatile (hydrosaline) system shows that brines can occur by direct magmatic immiscibility. The comprehensive hydrothermal evolution suggests a nearly isobaric cooling path, with local boiling episodes in the miaroles, probably in coincidence with invasion of external waters.

Frezzotti, M. (1992). Magmatic immiscibility and fluid phase evolution in the Mount Genis granite (southeastern Sardinia, Italy). GEOCHIMICA ET COSMOCHIMICA ACTA, 56(1), 21-33 [10.1016/0016-7037(92)90114-X].

Magmatic immiscibility and fluid phase evolution in the Mount Genis granite (southeastern Sardinia, Italy)

Frezzotti, M.
1992

Abstract

The Mount Genis granite is one of the post-tectonic intrusives emplaced late in the magmatic history of the Hercynian batholith in Sardinia. Devitrified silicate melt inclusion are present in some (magmatic) rock-forming and miarolitic quartz. These magmatic remnants show initial melting at 680-720-degrees-C. High-temperature observations (700-800-degrees-C) revealed the presence in some of the inclusions of mixed hydrosaline melt (Li) and silicate melt (L2), with extremely variable L1/L2 ratios. Electron microprobe analyses indicate LI to be K-Na dominated chlorides. Inclusions of mixed silicate and hydrosaline melts are interpreted to have been formed by heterogeneous trapping of two immiscible fluid phases (silicate-hydrosaline) after second boiling, most likely during the final crystallization stage. Magma-derived brines (63 eq wt% NaCl) circulated at subsolidus conditions from almost-equal-to 600-degrees-C and were retained in the miarolitic cavities down to about 400-degrees-C. Fluid unmixing occurred locally in the miarolitic cavities from 550-degrees to 412-degrees-C. At temperatures of almost-equal-to 400-degrees to 100-degrees-C the microgranite was invaded by diluted waters (almost-equal-to 4-5 cq wt% NaCl). A possible model for fluid evolution begins with a hydrosaline melt exsolving from the magma at the late-magmatic stage. The absence of boiling within the volatile (hydrosaline) system shows that brines can occur by direct magmatic immiscibility. The comprehensive hydrothermal evolution suggests a nearly isobaric cooling path, with local boiling episodes in the miaroles, probably in coincidence with invasion of external waters.
Articolo in rivista - Articolo scientifico
Granite, petrology, magmatic fluids
English
21
33
13
Frezzotti, M. (1992). Magmatic immiscibility and fluid phase evolution in the Mount Genis granite (southeastern Sardinia, Italy). GEOCHIMICA ET COSMOCHIMICA ACTA, 56(1), 21-33 [10.1016/0016-7037(92)90114-X].
File in questo prodotto:
File Dimensione Formato  
2) Frezzotti 1992.pdf

Solo gestori archivio

Dimensione 7.25 MB
Formato Adobe PDF
7.25 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/174660
Citazioni
  • Scopus 74
  • ???jsp.display-item.citation.isi??? 75
Social impact