Harris Creek Subdistrict

The Harris Creek Subdistrict is located on the northwest side of the Rock Creek Graben. It is named for the local stream called Harris Creek (Figure 25). Both the Annabel Lee and the Denton Mine are located in this Subdistrict. The Goose Creek Mines are sometimes grouped with the Harris Creek Subdistrict, but usually the two considered two separate Subdistricts.

Mines in the Harris Creek Subdistrict

Denton Mine

The Denton Mine, owned by the Ozark-Mahoning Company, was located in the southwest portion of the Harris Creek Subdistrict (Figure 25). The shaft was completed in 1980, and production probably began in 1981 (Morse 1981). The main production shaft was 688 feet deep, and several other shafts were present for ventilation and escape routes. The ore was of the bedding replacement type and was similar to the ore in the Cave-in-Rock Subdistrict. The main ore-body at the Denton Mine was located on the Rosiclare (Aux Vases) and Bethel Levels, but three other levels were also mined. Substantial ore was also mined from northeast-trending parallel trends accessed by crosscuts from the main orebody. One pod, northwest of the main orebody, mined the Rosiclare Level, and the second, southeast of the main orebody, mined both Rosiclare and sub-Rosiclare ores. In addition, a rich isolated pod of Rosiclare and sub-Rosiclare ores was mined about 200 feet northeast of the shaft (Ross Lillie, personal communication with Brett Denny, 2018). The ore followed northeast–southwest fractures and extended in a linear fashion. Spry et al. (1990) examined the fluid inclusions in fluorite crystals from the Denton Mine. They determined that several different fluids mixed to form the ore deposits and suggested that the fluids were primarily basinal brine type. Spry et al. (1990) also measured a 2 per mil (2‰) depletion in the δ18O values of limestone host rock forming a halo surrounding the ore deposit. The authors attributed this depletion to temperature variations and fluid exchange between the ore-forming solution and the limestone host rock. John Nelson and Donald K. Lumm of the ISGS made a brief underground tour of the Denton Mine in 1982. The working level visited was in the uppermost Ste. Genevieve Limestone beneath the Rosiclare (Aux Vases) Sandstone. Ore-grade material followed a northeast-trending belt of fractures about 75 to 150 feet wide. From a skip shaft 650 feet deep, mining proceeded in a room-and-pillar pattern. As Nelson observed in field notes, “The ore replaces limestone in roughly horizontal, lenticular bodies that have undulating to crenulated bands of alternating yellowish fluorspar, purple spar, and white to yellowish-brown calcite separated by layers or lenses of unaltered limestone.” This style of mineralization is commonly called coontail. In several places, limestone had collapsed in V-shaped zones striking northeast, parallel to the outlines of the orebody. Such zones could be as wide as 40 feet and as deep as 30 feet and contained exceptionally high-grade, coarsely crystalline ore. The northeast-trending fractures that evidently carried ore-bearing fluids were inconspicuous and showed little or no displacement. The Denton Mine closed in 1994 (Miller 1995). Ozark-Mahoning files indicate that 967,503 raw tons of ore was extracted from this mine. More Information: 10082972

Annabel Lee Mine

The Annabel Lee Mine, operated by the Ozark-Mahoning Company, was located northeast of the Denton Mine just west of Illinois Route 1 (Figure 25). The name alludes to the poem Annabel Lee by Edgar Allan Poe, in which the poet mourns for his lost lover “in her sepulchre there by the sea.” The headframe is still standing and can be observed from Illinois Route 1. The main shaft was completed in 1984 and was nearly 1,000 feet deep. The Annabel Lee ore pods were narrow, commonly less than 100 feet wide, and ran parallel to the major northeast–southwest structure of the Rock Creek Graben. The ore was mainly on the Rosiclare Level, but four other ore levels were mined. The ore within the sub-Rosiclare Level occurred in lenticular masses ranging from a few inches to 12 feet thick. Tilted and jumbled, angular clasts of limestone were embedded, indicating large-scale dissolution that created open cavities. Open voids as wide as several feet were numerous. Calcite and fluorite formed very large crystals, whereas most of the sphalerite was finely to coarsely crystalline. Narrow, planar fractures trending northeast were present but not conspicuous or consistent in spacing. In 1986, the ore from the Bethel Level averaged about 40% CaF2, whereas the ore from the sub-Rosiclare Level was slightly lower grade. Ozark-Mahoning ore reserve sheets from 1993 indicate that ore from this mine averaged about 30% to 35% CaF2 and 2% to 5% zinc. In 1990, Ozark-Mahoning geologists estimated that ore from the Annabel Lee equaled 961,084 raw tons, and other Ozark-Mahoning documents indicate that 868,000 raw tons was extracted. They also suggested that mineralization might extend northeast to the Saline River. When the mine closed in 1996, it was the last working fluorspar mine in Illinois. According to Dan Pilcher, the mine superintendent, bedding replacement ore was worked from several levels: the Bethel Sandstone, Levias Limestone, Rosiclare (Aux Vases) Sandstone, sub-Rosiclare, Lower Rosiclare, and St. Louis (“Cadiz,” explained below). Geologists John Nelson and Jim Baxter from the ISGS toured the St. Louis Level in 1988 and described crudely banded ore comprising alternating layers of calcite of various colors with fluorite and sphalerite on the St. Louis Level. They observed many vugs one foot or more across and vertical to steeply inclined fissures lined with large, well-formed crystals. On the basis of their lithological observations underground, both Nelson and Baxter questioned whether the country rock was St. Louis Limestone and speculated that it really was within the Ste. Genevieve Limestone. Because of the misleading correlation with the St. Louis Level, Ross Lillie proposed the name “Cadiz” for this working level, stating that the level was near the base of the Ste. Genevieve Limestone. The term St. Louis Level is misleading because the level is actually in the Ste. Genevieve. Therefore, the new term “Cadiz” is preferred for this level. More Information: 10082956

References

Miller, M.M., 1995, Fluorspar, in Minerals yearbook 1994: Volume 1, Metals and minerals: U.S. Department of the Interior, Bureau of Mines, 5 p.

Morse, D.E., 1981, Fluorspar, in R.C. Horton, ed., Minerals yearbook 1980: Metals and minerals, Volume I: U.S. Department of the Interior, Bureau of Mines, p. 321–334.

Spry, P.G., M.S. Koellner, C.K. Richardson, and H.D. Jones, 1990, Thermochemical changes in the ore fluid during deposition at the Denton Mine, Cave-in-Rock fluorspar district: Economic Geology, v. 85, no. 1, p. 172–181.