Geology and geochemistry of the Santa Eulalia mining district, Chihuahua, Mexico
AuthorMegaw, Peter Kenneth McNeill
KeywordsGeology -- Mexico -- Chihuahua Region (Chihuahua)
Geochemistry -- Mexico -- Chihuahua Region (Chihuahua)
AdvisorTitley, Spencer R.
Committee ChairTitley, Spencer R.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractSanta 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.
Degree GrantorUniversity of Arizona
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Old Colony and General Conference Mennonites in Chihuahua, Mexico: History, representations and women's everyday lives in health and illnessNichter, Mark; Reinschmidt, Kerstin Muller (The University of Arizona., 2001)During the early 1920s, Old Colony Mennonites emigrated from Canada to Chihuahua, Mexico in order to continue their traditional ways of life in nearly isolated, agricultural communities. As their ancestors had done for centuries, they continued to live in opposition to "the world." While the Old Colony Mennonites basically succeeded in living their distinct, conservative ideology, economic necessities and real world opportunities caused internal disagreements, excommunications and the formation of a new, liberal church, the General Conference, among their midst. North American Mennonite and some European scholars have recorded the history, political economy, socio-religious organization, linguistic and cultural characteristics of these so-called "Mexican Mennonites." What their large-scale perspectives have failed to capture is the everyday lives of the cultural group, the lives of women in particular. Women's worlds have been invisible in the official discourse on Mennonite history, most of which is male-dominated. This dissertation explores the everyday lives of Mennonites in the colonies near Cuauhtemoc, Chihuahua through Mennonite women's eyes. Women's multiple roles at the household level in times of health and illness, and women's moral identities are its focus. Women's habitus and discourses are central in perpetuating Mennonite gendered and moral identities. These identities, expressed in everyday moral living, are the foundation to Mennonite women's health work and local meanings of health. The ethnographic descriptions of women's lives demonstrate how ideology becomes operationalized, and the contrasting of existing literature with my findings exemplifies the articulation of ideology and gender. As an understanding of local Mennonite women's lives requires an appreciation of Mennonite history, socio-economic structure, and the values and norms reproduced by women during their everyday lives, this dissertation has a comprehensive, four-fold structure: Part I summarizes the history of the Mennonites near Cuauhtemoc and analyzes its representational politics; Part II lays out the anthropological processes of fieldwork and writing; Part III describes the contemporary everyday lives of Mennonite women with a focus on their gendered work, including health work, and socializing practice; Part IV discusses the socialization processes of Mennonite women, inherent challenges in Mennonite social structure, and the ways in which Mennonites cope with these challenges.