| Description |
x, 68 leaves : illustrations, photographs ; 29 cm |
| Summary |
"Fluid inclusions in successively deposited generations of sphalerite from the Tri-State district have been examined for geothermometry as a function of time. The main stage of vug-filling sphalerite has been studied most intensively and as many as 83 fluid inclusions have been examined in a single crystal. These sphalerite crystals are commonly zoned, and their filling temperatures exhibit a general pattern of declining temperature from their cores outward, from about 135°C down to 90°C. The decline is not a steady one, but rather it is characterized by fluctuations commonly about 15-20°C. Some fluctuations have magnitudes as great as 50-60°C, with temperature peaks reaching as high as 160°C. Earlier deposited yellow disseminated sphalerite was formed in a narrow temperature interval, 120 to 85°C, a range lower than that of the earliest main stage sphalerite. Small, reddish brown sphalerite, deposited after main stage sphalerite, appears to have formed at about the same or slightly higher temperature than the late portions of the zoned sphalerite crystals. The fluctuations in temperatures of deposition between generations of sphalerite and throughout a single period of sphalerite deposition indicate a fluctuating character of the ore-forming fluid. The fluctuations may be the result of multipulse introduction of the ore fluid or of mixing with a cooler fluid"--Abstract, leaf ii. |
|
