Abstract The Greenstone Resources Santa Rosa mine is located in central Panama about 200 km southwest of Panama City. The mine was the largest producer in Central America, but production was temporarily suspended in February 1999 with less than 5 million tonnes (Mt) of remaining reserves at a grade of 1.9 g/t Au ($300/oz). An integrated structural analysis was performed to determine the primary ore controls within the Santa Rosa deposit. The primary control is fault-related fracturing, particularly those fractures associated with the Santa Rosa fault. Although far less important, secondary controls relate to the permeability of the various pyroclastic, epiclastic, and intrusive host rocks. The methodology and results of the integrated structural analysis are described in the text to familiarize the reader with this technique. The application of the integrated structural analysis process was used to identify exploration characteristics that could be used for the field identification of exploration targets. The best set of exploration pathfinder elements were identified, visual field characteristics associated with ore mineralization were described, the optimum drill hole orientation was defined, and individual targets were identified and prioritized. Production issues were also addressed such as slope stability within the Alto de la Mina pit and grade control. Four separate deformation events were identified from a database collected from within the two pit areas and surrounding outcrop exposures. The earliest deformation event produced the Santa Rosa fault, and provided conduits for the intrusion of a porphyritic basalt stock and later latite dikes. Injection of the latite dikes adjacent to porous, wet volcaniclastic debris piles produced a series of funnel-shaped di-atreme pipes resulting from phreatomagmatic eruptions. Fragments of the latite are abundantly incorporated within the diatreme pipes Subsequent movement along the Santa Rosa fault produced additional steeply raking, strike-slip-controlled conduits for later mineralizing solutions during gangue and ore-metal deposition. The main quartz and sulfide deposition occurred during the second deformation event and the precious metals and associated pathfinder elements came into the system during the third deformation event. The fourth event was barren and offset the upper part of the orebody in the Alto de la Mina pit with reverse movement. Ore is typically found within the diatreme pipes or directly adjacent to the Santa Rosa fault plane in the basalt porphyry. With few exceptions ore is found within several tens of meters from the fault, but in one instance in the A zone of the Santa Rosa pit, ore extends to as much as 300 m from the main fault. This distal ore developed during the third deformation event where the fluids were conducted along an earlier reactivated set of northeast fractures created during the first deformation event. The ore produced here is lower grade than the ore adjacent to the main fault, presumably due to the enhanced fluid flow and resultant better availability of ore metals nearer the primary conduit. Strike-slip movement along the Santa Rosa fault dominated the kinematics of the first three deformation events. Inflections in the Santa Rosa fault conduit from its shear direction toward the extensional direction typify the ore zones in both pits. At these strike inflections, ore-related movement along the fault generates a zone of open conduits where associated extension fracture splits and cymoid loops enhance the permeability in the zones. The increased permeability along the fluid conduits controlled the amount of silica flooding. Gold in the form of electrum is often contained within very late crosscutting clear quartz stringers or adjacent to grains of pyrite. Where fluids deposited gold in nonsilicified sediments such as in the A zone orebody of the Santa Rosa pit, grades are significantly lower than the silicified, diatreme-hosted ore of the Alto de la Mina pit. The overall grade of the diatreme-hosted Alto de la Mina ore is higher than the volcaniclastic-hosted Santa Rosa ore at 2.0 g/t Au and 1.4 g/t Au, respectively.

Abstract Gold mineralization in the Veraguas gold belt of Panama is hosted by calc-alkaline volcanic rocks of mid-Miocene age. Volcanic rocks range in composition from basalt to rhyolite and are intruded by coeval dikes, plugs, and exogenous volcanic domes of the same composition. Pyroclastic aprons surround the domes and host gold ore deposits. The Remance mine, a vein and vein stockwork, has produced gold intermittently for over a century. Santa Rosa, a shallow epithermal stockwork and disseminated deposit, went into production in 1995. The geologic setting of these deposits draws attention to the exploration potential of volcanic dome fields and related shallow epithermal (hot spring) systems throughout Central America.

Abstract Heavy oil deposits 11 km (7 mi) north of the town of Santa Rosa, Guadalupe County, New Mexico, in the Triassic Santa Rosa Sandstone, were mined during the 1930s. Renewed interest in this deposit in the late 1970s so far has not resulted in exploitation because of unfavorable economics and the encroachment of man-made Santa Rosa Lake. The Santa Rosa Sandstone in east-central New Mexico is from 35 to 108 m (115-355 ft) in thickness and consists of light-brown to gray, cross-bedded, medium- to coarse-grained sandstone, and subordinate brown and red mudstone. The sedimentary section below the Triassic includes strata of Permian, Pennsylvanian, and Mississippian age, with an aggregate thickness of about 1830 m (6000 ft) resting on Proterozoic basement. These rocks have a regional dip of a few degrees to the southeast. Organic geochemical analyses characterize the oil as a moderately immature, naphthenic oil that has undergone extensive bacterial degradation. Several geochemical properties point to the Permian San Andres Formation or Pennsylvanian strata as the most likely source rock. Migration of the oil may have taken place along sinkholes or faults, whereas distribution of the bituminous material within the sandstone has been controlled by local variation in porosity and permeability. Updip migration and bacterial action led to the accumulation of extra-heavy oil near the surface.

Abstract The Guanajuato Mining District covers an area 20 km long by an average of 16 km wide located 475 km northwest of Mexico City in the approximate center of Guanajuato State (Fig. 1). It includes the La Luz area on the west, Peregrina-El Cubo on the east, and Santa Rosa to the northeast (Fig. 2). The town of Guanajuato occupies a narrow valley almost at the center of the district, at 21°0r01″N and 101°15′20″W. The mining district connects with Highway 57 by way of Dolores Hidalgo and San Luis de La Paz; and with Highway 45 by way of Silao. The Guanajuato-Silao railroad branch connects the district with the main México-Ciudad Juárez line. A smallcraft airport (Los Infantes) is about 18 km south of Guanajuato on the road to Irapuato; commercial airlines fly to Mexico City from the town of León, on Highway 45, 62 km west from Guanajuato. A 3.2-km all-weather dirt road from La Olla Dam in Guanajuato City to Mineral del Cubo leads to the Torres-Cedros Mine, the largest producer in the district.

Abstract The Guanajuato mining district is located in the central part of the state of Guanajuato, 475 kn1 northwest of Mexico City (Fig. 1). The district has an approximate length of 20 km and a width of 16 km, and includes the mining areas of La Luz to the west, Santa Rosa to the north, and Peregtina-El Cubo to the east (Fig. 2). The city of Guanajuato is located at the center of the district. Guanajuato can be reached by paved highways, railroad, or by commercial plane (by way of León airport, 62 km from Guanajuato city). The Torres-Cedros mine, which has the greatest production in the district, is located 3.2 km from the city and can be reached by a dirt road.