Photomicrographs of different types of multisolid inclusions (type 4) within the recrystallized quartz (Q1N). The marked phases were identi fi ed by Raman (LRMS). 

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... the inclusions is variable (negative crystal shapes being the most common). Some inclusions contained 1 or 2 birefrigent crystals identi fi ed by Raman spectroscopy as nahcolite and calcite (Fig. 6). These solids can be found in about 25 – 40% of all the type 1 inclusions, but can easily be overlooked. In inclusions that look unaffected by recrystallization and/or leakage, the volume occupied by nahcolite and calcite crystals is relatively constant (~5 vol.%). In a few type 1 inclusions, other unidenti fi ed solids were sporadically present. The relatively constant volume ratio of nahcolite crystals in type 1 inclusions may be considered to be circumstantial evidence for their daughter nature. The apparent absence of nahcolite in some inclusions may re fl ect kinetic dif fi culties associated with nahcolite nucleation. We have noticed nahcolite nucleation after a cooling (freezing) cycle in a few inclusions. The partial homogenization of the carbonic phase (Th(car)), almost always to a liquid (L car +V car → L car ), ranges between − 21.6 °C and 29.5 °C. Final melting of solid CO 2 (Tm(car)) occurs between − 56.6 °C and − 64.1 °C and the fi nal clathrate dissolution Tm(Cla) occurs between 8.3 °C and 12.3 °C. Systematic variation of Th(car) was observed in individual quartz grains in some samples: grain cores usually show the highest Th(car) values, while the rims exhibit the lowest ones (Fig. 7). The majority of the inclusions decrepitated shortly before their fi nal fl uid homogenization or immediately after this temperature. Some inclusions homogenized at 280 – 315 °C (Th(total), usually to vapor). The observed dissolution temperature of nahcolite is within 80 – 90 °C. The calcite crystals trapped in the same inclusions do not dissolve until the inclusion decrepitation at about 255 °C. Type 2 inclusions (Fig. 4) are predominantly hosted by recrystallized quartz (Q1N), typically in the form of sparse 3D-distributed inclusions, possibly of primary origin (with respect to Q1N). Type 2 inclusions also rarely form secondary trails in relic quartz (Q1Ur). Of all type 2 inclusions present in a sample, usually those hosted by quartz enclosed inside a sulphide matrix (pyrite and/or pyrrhotine) were the largest and thus the most suitable for microthermometry (Fig. 2). Type 2 inclusions are always two-phase (aqueous liquid + carbonic vapor) at room temperature, are 3 to 70 μ m in size (commonly 10 – 25 μ m), and display regular or negative crystal shapes. The volume fraction of the aqueous liquid is 0.5 ± 0.2. Similarly to type 1 inclusions, one or more solid phases (nahcolite and/or carbonate) were identi fi ed and are present in 50 – 70% of type 2 inclusions. With respect to the density of the gaseous phase, two subtypes can be de fi ned. High density type 2 (TYPE 2a): Tm(car) from − 66.2 to − 60.0 °C (however not measurable in every inclusion), Th(car) from − 49 to +20 °C (always to L), and Tm(Cla) from +10.8 to +18.5 °C. Low-density type 2 (type 2b): the gas content of inclusions did not freeze even down to − 196 °C. Th(car) occurred from − 80 to − 11 °C (always to V) and Tm (Cla) from +14.3 to +19.5 °C. The inclusions probably correspond to the H 2 type of the Van den Kerkhof (1990) classi fi cation. Apart from the density, there is no difference in the size, shape, distribution and volume fraction of the aqueous phase of type 2a and type 2b inclusions. We are not able to separate type 2a and 2b inclusions by petrographic criteria alone. Therefore we cannot exclude that they represent two separate and genetically different inclusion types. The fi nal homogenization /Th(total)/ could not be measured due to partial leakage of majority inclusions above 250 °C (type 2a). In most inclusions, nahcolite remained in the inclusions up to their decrepitation without any evidence of dissolution. Only occasionally melting of nahcolite was observed between 84 °C and 90 °C. Important variations of the CO 2 /CH 4 ratio were found in both subtypes. However, there is no correlation between this parameter and the inclusion distribution at the grain scale (in contrast to type 1 inclusions in Q1Ur). Type 3 inclusions (Fig. 4) are secondary and mostly form short intragranular trails in Q1Ur and Q1N quartz. Rare trails crosscutting grain boundaries between quartz Q1Ur and Q1N were also found. Inclusions are two-phase (aqueous liquid + aqueous vapor) at room temperature, mostly oval shaped and show homogeneous volume fraction of aqueous liquid (0.9 – 0.95). The temperature of the fi rst/ initial melting (Ti) is from − 44 to − 37.0 °C and the fi nal melting of ice (Tm(Ice)) is between − 4 and − 1 °C, indicating that calcium is the main cation. There is no microthermometric evidence for the presence of gases. The total homogenization temperature (Th(total), usually to liquid) shows three maxima around 140, 180 and 260 °C. We have found numerous single-phase to multi-phase solid inclusions inside grains of recrystallized quartz Q1N (Fig. 5). Occa- sionally, a volumetrically insigni fi cant fl uid phase was also identi fi ed. Some solids are very dif fi cult to recognize or even to see by optical microscopy using a classical bright fi eld. Very careful observation incorporating both plane and crossed polarization was necessary to observe their presence. Type 4 inclusions (up to about 150 – 200 μ m in size) usually consist of 3 to 10 solid phases. Based on their petrographic criteria, they are considered primary with respect to Q1N. The most frequent solid phases (identi fi ed using Raman microspectroscopy) are chlorite, calcium carbonate and albite, with a size that usually varies from 20 to 50 μ m. Other solids (muscovite, rutile, pyrite, apatite, titanite, anatase ± some unidenti fi ed solids) occur randomly in different inclusions. It seems that there is a correlation between the number of type 4 inclusions present in the individual samples and the depth of the sample in the mine (i.e. distance to the granodiorite contact). The samples closest to the contact generally contain the highest number of multisolid inclusions. The fl uid phase (gas, aqueous or both) mostly wets the surface of the solids, which makes its optical identi fi cation dif fi cult and explains the absence of microthermometric data for these inclusions. However, H 2 O, CO 2 , CH 4 , N 2 , and H 2 were identi fi ed using Raman microspectrometry (see Section 6). Quantitative gas content measurements were performed on series of about 40 fl uid inclusions representing the primary inclusions (type 1) in the original quartz (Q1Ur) and the primary inclusions (type 2) in the recrystallized quartz (Q1N). Selected representative measurements are presented in Tables 1 and 2. Type 1 inclusions show (H 2 O) – CO 2 – CH 4 (±N 2 , H 2 S) composition with CO 2 as the main gas compound (98 to 89 mol% of gas content), CH 4 between 0.6 and 10 mol% and traces of N 2 and H 2 S around 0.5 and 0.1 mol%, respectively. Type 2 inclusions contain traces of C 2 H 6 , in addition to (H 2 O) – CO 2 – CH 4 (±N 2 , H 2 S). The variations in the CO 2 /CH 4 ratio are far more noticeable than in type 1 inclusions. The CO 2 concentration varies from 95 mol% to 14 mol% and CH 4 varies from 5 mol% to 86 mol%. The concentrations of N 2 and H 2 S are almost constant, around 0.5 and 0.1 mol%, respectively. C 2 H 6 is constantly present at trace levels (0.1 mol%) and was identi fi ed from its Raman peaks (C – H stretching at 2955 cm − 1 and C – C stretching at 990 cm − 1 ) (Fig. 6). No evidence for precipitated carbon inside the inclusions was found by LRM. Type 4 inclusions: the composition of the volumetrically accessory fl uid phase is highly variable — from nearly poor CH 4 in some cases to CH 4 – CO 2 mixtures (with or without H 2 O). In some inclusions, H 2 was identi fi ed (Fig. 6) in concentrations as high as 6 mol% (calculated using the standard methodology as described in Dubessy et al. (1989)). The aqueous phase was also checked for the presence of polyatomic ions, such as CO 2 3 − , HCO − 3 , SO 4 , PO 3 4 − and HS − , which are Raman active, permitting their identi fi cation and analysis in the fl uid phase (Rosasco and Roedder, 1979; Dubessy et al., 1983,1989). HCO − 3 in the aqueous phase of type 1 and type 2 inclusions was identi fi ed by its Raman peaks at 1013 cm − 1 and 1362 cm − 1 (Davis and Oliver, 1972; Oliver and Davis, 1973; Kruse and Franck, 1982; Frantz, 1998) (Fig. 6) which were obtained even with small integration times (2 s), indicating a high concentration around 1 mol/l. Dissolution of nahcolite at 80 – 90 °C indicates NaHCO 3 concentrations around 2 mol/l NaHCO 3 (Kogan et al., 1969; Vapnik and Moroz, 2002; Haynes, 2003). High-temperature Raman measurements also indicated the presence of HCO − 3 in solution after homogenization of selected inclusions at 326 °C. Calculation of the bicarbonate ion concentration from the Raman spectra is under development, so we were not able to quantify it precisely. These estimations suggest that HCO − 3 is probably the main anion in the solutions. In spite of the fact that only 25 – 40% of the inclusions demonstrably contain nahcolite crystals, the authors assume the nahcolite is of primary (i.e. daughter) origin, based on the relatively constant crystal/inclusion volume ratio (see above) and on the Th(total) of the fl uids over 300 °C which (most likely) excludes the presence of solid (i.e. trapped) nahcolite (Hoshino et al., 2006). The dissolution temperature of nahcolite in type 2 inclusions is highly variable, from 84 – 90 °C usually to above 250 °C, without any evidence of dissolution at this temperature. High dissolution temperatures can be interpreted either by high concentrations of bicarbonate, trapping of nahcolite together with the fl uid, or by metastability. According to previous data on fl uid inclusions, dissolution temperature around 80 °C in type 1 inclusions and industrial dissolution plants of nahcolite deposits, the ...

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... have found numerous single-phase to multi-phase solid inclusions inside grains of recrystallized quartz Q1N (Fig. 5). Occa- sionally, a volumetrically insignificant fluid phase was also identified. Some solids are very difficult to recognize or even to see by optical microscopy using a classical bright field. Very careful observation incorporating both plane and crossed polarization was necessary to observe their ...