Santa Eulalia contains two separate, contrasting Pb-Zn-Ag deposits. The East Camp consists of a symmetrically zoned calc-silicate skarn with distal sulfide and tin-bearing orebodies; whereas the west Camp is composed of massive sulfide orebodies with minor proximal calc-silicate skarn and isolated intermediate calcic-iron skarns. Mineralization and alteration are zoned within each camp but do not overlap. Sulfide mineralization in both camps consists of pyrrhotite, sphalerite, galena, and pyrite with lesser amounts of arsenopyrite and chalcopyrite. The East Camp is apparently richer in zinc and copper than the West camp. Mineralization is temporally and spatially related to geochemically identical felsite intrusions which apparently have a common source. Mineralizing fluids followed these felsites through a thick section of evaporites and organic-rich shaly limestones into clean, homogeneous, relatively undeformed, limestone hosts. West Camp mineralization occurs along an interconnected network of vertically discontinuous tight fissures and sill contacts, whereas East Camp mineralization is located along vertically throughgoing faults and dike contacts. strata-bound, but not stratiform, mantos extend off discordant chimneys in both camps. Ore textures reveal that mineralization occurred primarily by limestone replacement. 21 Pressure-corrected primary fluid inclusion homogenization temperatures in fluorite range from 220 to 490 deg. C. Salinities are bimodal with high-salinity (>26.3 equivalent wt% NaCl) and low-salinity (1-12 equivalent wt% NaCl) populations. Mineralogical constraints indicate that the hydrothermal fluids were acid and reduced. Sulfur isotope analyses indicate that the ore fluids varied from -17 to +4 permil without correlation to iron-sulfide species, temperature, or salinity. Co-existing sulfides are commonly in isotopic disequilibrium. Sulfur isotopes from the West Camp are crudely zoned, but no consistent patterns exist in the East Camp. Oxygen and carbon isotope analyses of limestone wallrocks reveal a distinct isotopic alteration halo. A single analysis of gangue calcite from each camp indicates that the ore fluids contained non-carbonate-derived carbon and oxygen, possibly of magmatic origin. Metals were apparently transported as chloride complexes and deposited through coupled dissolution-precipitation replacement reactions. Most ore sulfur apparently came from diagenetic pyrite and sedimentary anhydrite, but some of the sulfur may have had a magmatic source. The metals probably came from the felsite parent magma and this magma may have also contributed fluids. Close similarities between Santa Eulalia and numerous other intrusion-related carbonate-hosted deposits in northern Mexico reinforce these interpretations.

Three previously unrecognized outcrops of pre-Carboniferous rock in the Mina Plomosas - Placer de Guadalupe area have a total area of slightly less than four square miles. Six units, ranging in age from Ordovician to Jurassic, are mapped within the Plomosas Formation named by Burrows in 1909; the total thickness is about 8,000 feet. The lower 2,000-foot section of Ordovician, Silurian, Devonian, Mississippian, and Pennsylvanian rock, composed predominantly of limestone, resembles contemporaneous formations in west Texas. The 2,000-foot to 3,000-foot section between Pennsylvanian and Late Jurassic rock, composed predominantly of siltstone and conglomerate, consists of a 500-foot to 1,000-foot Permian (Wolfcampian-Leonardian) sequence overlain by beds of undetermined age. The Permian sequence includes a reef. The 3,000-foot section of Late Jurassic rock is composed of shale, sandstone, and limestone. The area lay to the north of the main Ouachita trend, and Paleozoic tectonism was less intense than in the Marathon uplift. Nevertheless, angular unconformities within the Permian sequence indicate Permian movements. Laramide tectonism was extreme, with major overthrusting toward the west. Two large sections are upside-down. Crustal shortening on the order of ten miles can be proved near Mina Plomosas. Probably the sericite and microspar (finely recrystallized limestone), in the Paleozoic and Jurassic rocks, are products of incipient metamorphism resulting primarily from Laramide deformation. Mina Plomosas is an important lead-zinc mine. A little placer gold is found at Placer de Guadalupe. All mineralization in the Placer de Guadalupe - Mina Plomosas area is thought to be Tertiary in age. The petroleum potential of Chihuahua is still untested. / text

Tesis doctoral--Austin--Universidad de Texas, [1975]. / Publ. pour la première fois en anglais en 1975. Notes bibliogr. p. 232-235.

No description available.

The geologic map of El Cuervo area shows distribution of stratigraphic units ranging in age from Jurassic (?) to Recent. Outcropping strata are principally Cretaceous in mountainous areas and Cenozoic in bolson areas. From the Late Jurassic Epoch until the Late Cretaceous Epoch the Chihuahua Trough was a negative feature with respect to adjacent platforms and 10,000 to 18,000 feet of Jurassic-Comanchean sedimentary rock, including a thick basal evaporate sequence, accumulated in it; whereas on the adjacent Diablo Platform of Texas about 3,000 feet of sedimentary rock accumulated. The lower part of the Mesozoic sedimentary record shows a gradual transgression, interrupted by numerous minor regressions, from the Chihuahua Trough onto the Diablo Platform. The upper part of the record shows a regression. The eastern edge of a Jurassic (?) evaporite basin is in the eastern part of the area. Neocomian-Aptian formations are dominantly siliciclastic. Middle Albian formations are dominantly siliciclastic in the eastern part of the area, but are predominantly shallow-water carbonate to the west. Late Albian-early Cenomanian formations are limestone with subordinate shale. During the Cenomanian Epoch siliciclastic deposition again became dominant and the medial Cenomanian-Senonian formations record a transition from marine to continental deposition. Mesozoic and Paleozoic "basement" rocks were deformed during the Late Cretaceous-Early Tertiary Laramide orogeny. Jurassic (?) evaporites acted as a décollement zone between Mesozoic and Paleozoic rocks. Major thrust faults, over-thrust toward the east, developed along the eastern edge of the evaporite basin in El Cuervo area. During thrust-faulting, evaporites were diapirically injected into younger rocks along thrust- and tear-fault zones. As evaporites flowed into diapirs and cores of anticlines, blocks settled differentially into space abandoned and chaotic patterns of normal faults resulted. Olivine-diabase sills and dikes and amphibole-rich rocks (where olivine diabase was intruded into and contaminated by evaporites) may have formed during early stages of Laramide deformation. During and after Laramide deformation denudation created a surface of erosion in the area. During Early Tertiary erosion as evaporites were removed, collapse structure developed over diapirs, which had been injected along tear-fault zones. At several places in near- vertical beds on flanks of folds, as erosion removed nonresistant beds, gravity developed flaps and detached flaps in adjacent resistant beds of limestone. During late Eocene-early Oligocene time flow rocks, ignimbrites, and associated sedimentary rocks were deposited in widely scattered, topographically low areas. Volcanic and associated rocks, deposited in collapse features, were deformed as erosion of evaporites continued and they foundered into evaporites. Two porphyritic andesite intrusions are associated with Laramide faults; one is in the core of a large anticline. In the southeastern part of the area several trachyte intrusions along east-trending joints formed dikes. Subsequent to vulcanism, the region was uplifted from elevations near sea level to thousands of feet above sea level and Late Tertiary block-faulting was superimposed on Laramide structure in the eastern part of El Cuervo area. Intrusion of olivine-biotite "peridotite" may have accompanied faulting or immediately followed the main episode of faulting. Thick sections of bolson fill were deposited in the Presidio and Benigno grabens as a consequence of block-faulting. Although some Laramide faults may have been reactivated during Tertiary block-faulting, major Tertiary faulting did not take place west of the eastern front of the easternmost range of the Chihuahua Tectonic Belt. / text

No description available.

No description available.

Examines the processes of disappearance during the late 16th and 17th centuries--through assimilation or extermination--of the native Indians encountered by Spaniards in present-day Chihuahua, Mexico.

No description available.

As a native of El Paso, Texas my work reflects on autobiographical narratives and violent events that have taken place along the US-Mexico border. For the past two years my research and artwork have focused on the Femicidios (women murders) in Ciudad Juárez (Chihuahua, Mexico). The specific case of Campo Algodón (2001), where eight young women were found in a mass grave in the center of the city, led me to investigate and produce a group of works in reference to loss, justice, memory and erasure. My purpose is to create works that inform the viewer of something that has occurred and continues to happen. My artistic approach involves concept, research and process, which eventually result in installations and sculptural objects. My aim in this thesis is to outline my research methodology and explore the intersections of my work with theoretical discourses in art, human rights, and neoliberalism. With a minimalist aesthetic, my work often masks the labor intensive process involved in research and production. By mining the archives of classified documents used in international human rights courts, I use this material as the base for my work. The nature of this material often dictates its visibility or illegibility as a classified source that cannot be revealed. This body of work requires collaboration across disciplines in which the research and communication with specialists have helped in the formation of each piece. / text