Many zinc-lead deposits of the Mississippi Valley type occur in northern Arkansas along the southern flank of the Ozark uplift. Geologically the deposits are similar to the much larger deposits in the Tri-State region 200 kilometers to the northwest. Studies of freezing and homogenization temperatures of fluid inclusions in minerals from the Arkansas deposits have been made to see if the ore fluids were also similar. Primary inclusions in sphalerite, quartz, and dolomite homogenized in the range 80 degrees to 132 degrees C. Pressure corrections to be added probably do not exceed 10 degrees C. Most of the primary inclusions in calcite were single phase, suggesting temperature of formation of less than approximately 50 degrees C. The majority of the freezing temperatures for sphalerite and quartz were in the range --20 degrees to --23.6 degrees C, corresponding to salinities greater than 22 weight percent salts; the highest freezing temperature for sphalerite was --10.8 degrees C, corresponding to approximately 15 weight percent salts. The freezing data for calcite show that calcite was deposited from solutions having salinities from less than 4 weight percent salts to nearly fresh water.The close similarity of the mineralogy, geology, and fluid inclusion data for the two districts suggests that they represent the same period of mineralization. The origin of the ore deposits may be explained by the movement of heated, saline, formational waters out of the Arkoma or Anadarko basins.

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