Very interesting question . Infact , in a pure calcite reaction having closed system, free access of carbon dioxide is disallowed ( very often called Turner effect ) , thereby , will have pH 8.0 to as high 11.0 , depending upon the intervention of carbon dioxide. But , in a calcareous soil , carbon dioxide most often comes into play , thereby , soil pH would be far lower .Please have a look at enclosed document..

Pure calcite may have pH around 8.1. But the pH of calcareous soils would depend on the climate. In sub-humid climate, a calcareous soil may show a pH values