In fluid inclusion homogenization and freezing temperatures were compared

In this study, prior to the microthermometry analyses, detailed petrographical studies based on the criteria represented by (Roedder, 1984; Goldstein and Reynolds, 1994, Van den Kerkhof and Hein, 2001), were conducted on the fluid inclusions in the single quartz crystal, which are either surrounded by or directly adjacent to the quartz-sulfides veinlets, to decipher the relationships and chronology between fluid inclusions and their host mineral.The majority of the isolated individual inclusions, random groups in intragranular trails of the quartz crystals as well as associated with solid (mineral) inclusions were interpreted as primary (FIs), whereas those aligned along healed fractures in transgranular trails cut across different quartz grain boundaries or intragranular clusters terminated by a crystal were considered as the secondary or pseudo secondary, respectively (Roedder, 1979; Roedder, 1984; Goldstein and Reynolds, 1994; Van den Kerkhof and Hein, 2001).Microthermometry measurements were mainly conducted on the abundant intragranular primary fluid inclusions assemblage (FIA), related to different stages of mineralization of the Haftcheshmeh PCD,  ranging from 5 to < 20 ?m in size having irregular, circular, or elliptical and negative crystal forms.

Data gathered from the fluid inclusion homogenization and freezing temperatures were compared to published data by Adeli et al. (2015). According to their compositions, visually identical phase proportion (L-V-S) at room temperature (25°C), phase transitions during microthermometry (-100 to >+550 0C) and laser Raman spectroscopy studies, which were carried out on more than 400 fluid inclusions, four compositional types of FIs have been distinguished in the quartz samples from various mineralization stages of the Haftcheshmeh PCD which are summarized in Table 3 and shown in Fig.

The main characteristics of each type of fluid inclusions are described below.Type I: Liquid-rich two-phase FIs (L-type), Vapor-rich two-phase FIs (V-type), Daughter mineral-bearing; D-type Fis and CO2-bearing liquid or vapour FIs; C-type.-       Liquid-rich two-phase FIs (L-type) consist of a dominant liquid phase (LH2O), a variable vapour bubble (VH2O) which occupies 5-45 % of total volume, and lack daughter crystals at room temperature.

The accidentally trapped minerals as a transparent and/or an opaque mineral generally present in all of them. The CO2 was not observed as a liquid or vapour phase in this type. However, the final melting of ice above 0°C in some of them, indicating the presence of a small amount of CO2 which could be distinguished by Raman spectroscopy. The shape of these inclusions generally varies from negative crystal to irregular shapes and range from 4 to 18 ?m in size. These inclusions always homogenize to the liquid phase upon heating. Co-existing liquid- and vapour-rich inclusions are very abundant, evidenced for boiling. Liquid-rich (L-type) inclusions are about 15 % of the total inclusion populations and found as scatters in the stage I to stage IV quartz veins with inconsistent proportions.

They are most abundant in Type B and D veins from phyllic and propylitic alteration zones and occur rarely in Type A-veins.Type II; Vapor-rich two-phase FIs (V-type) consist of a volumetrically dominant vapour phase which occupies more than 60% of the inclusion volume. In the vast majority of this type, the vapour bubble is more than 90% which could be caused difficulty in phase transition observation during microthermometric analysis. In many of the small size on or more accessory trapped minerals as halite and opaque minerals are observed.