A study of brittle deformation within a segment of the Hercynian intrusive complex of Gallura (comprising porphyritic biolite monzogranitic and granodioritic intrusions) reveals a quite regular network of fluid inclusion planes (interpreted as healed paleocracks) and open microcracks. Fluid inclusion planes and microcracks in 9 oriented samples show a consistent orientation across different intrusions; two principal, almost orthogonal sets have been recognized: N20-60-degrees-E-trending and N100-120-degrees-E-trending directions; both mainly consist of subvertical planes. A subhorizontal set is nearly always present as healed microcracks; it occurs as open cracks only in one sample. Microthermometric investigations on fluid inclusions show that Na dominated aqueous fluids (salinity from 0.9 to 12.3 wt.% NaCl eq.; ThL = 111-257-degrees-C) circulated throughout the intrusive complex, along almost all the microfracture sets during the late-stage hydrothermal history. Locally, subordinate Li- or Ca-, K- and Na-bearing brines have been detected along N100-degrees-E- and N160-degrees-E-trending paleocracks. Li-bearing brines have salinities ranging from 11 to 17 wt.% LiCl eq. and ThL from 74 to 171-degrees-C; salinity in Ca-dominated brines varies from 4.9 to 21.8 wt.% NaCl eq. and ThL from 130 to 217-degrees-C. The principal set directions (N20-60-degrees-E and N100-120-degrees-E) are often shared by fluid inclusion planes and open n-microcracks: it is suggested that they belonged to the same brittle deformation episode, related to late Hercynian batholith cooling and uplift

Giorgetti, G., Frezzotti, M., Ghezzo, C. (1992). Structural and microthermometric studies of fluid inclusions in the Gallura intrusive complex (N Sardinia). EUROPEAN JOURNAL OF MINERALOGY, 4(5), 1175-1185.

Structural and microthermometric studies of fluid inclusions in the Gallura intrusive complex (N Sardinia)

M. Frezzotti
;
1992

Abstract

A study of brittle deformation within a segment of the Hercynian intrusive complex of Gallura (comprising porphyritic biolite monzogranitic and granodioritic intrusions) reveals a quite regular network of fluid inclusion planes (interpreted as healed paleocracks) and open microcracks. Fluid inclusion planes and microcracks in 9 oriented samples show a consistent orientation across different intrusions; two principal, almost orthogonal sets have been recognized: N20-60-degrees-E-trending and N100-120-degrees-E-trending directions; both mainly consist of subvertical planes. A subhorizontal set is nearly always present as healed microcracks; it occurs as open cracks only in one sample. Microthermometric investigations on fluid inclusions show that Na dominated aqueous fluids (salinity from 0.9 to 12.3 wt.% NaCl eq.; ThL = 111-257-degrees-C) circulated throughout the intrusive complex, along almost all the microfracture sets during the late-stage hydrothermal history. Locally, subordinate Li- or Ca-, K- and Na-bearing brines have been detected along N100-degrees-E- and N160-degrees-E-trending paleocracks. Li-bearing brines have salinities ranging from 11 to 17 wt.% LiCl eq. and ThL from 74 to 171-degrees-C; salinity in Ca-dominated brines varies from 4.9 to 21.8 wt.% NaCl eq. and ThL from 130 to 217-degrees-C. The principal set directions (N20-60-degrees-E and N100-120-degrees-E) are often shared by fluid inclusion planes and open n-microcracks: it is suggested that they belonged to the same brittle deformation episode, related to late Hercynian batholith cooling and uplift
Articolo in rivista - Articolo scientifico
Petrology, Fluid inclusions, granite
English
1175
1185
11
Giorgetti, G., Frezzotti, M., Ghezzo, C. (1992). Structural and microthermometric studies of fluid inclusions in the Gallura intrusive complex (N Sardinia). EUROPEAN JOURNAL OF MINERALOGY, 4(5), 1175-1185.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/186242
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