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all geography including DSDP/ODP Sites and Legs
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Asia
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China
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Guizhou China (1)
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Guerrero Terrane (1)
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Jalisco Mexico (1)
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Moctezuma Mexico (1)
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Sierra Madre del Sur (2)
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Sierra Madre Occidental (29)
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Sonora Mexico (9)
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Trans-Mexican volcanic belt (2)
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North America
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Rocky Mountains
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Oceania
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Mariana Islands (1)
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Pacific Ocean
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East Pacific
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Gulf of California (10)
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Tamayo fracture zone (2)
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North Pacific
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Gulf of California (10)
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Middle America Trench (1)
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Tamayo fracture zone (2)
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Northwest Pacific
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Izu-Bonin Arc (1)
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West Pacific
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Northwest Pacific
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Pacific region
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O-18 (1)
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O-18/O-16 (2)
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Sm-147/Nd-144 (1)
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rhyodacites (1)
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sheet silicates
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Primary terms
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Asia
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Far East
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China
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Guizhou China (1)
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Atlantic Ocean
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North Atlantic
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Caribbean Sea
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Yucatan Basin (1)
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bibliography (1)
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Canada
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Western Canada (1)
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Caribbean region (1)
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Cenozoic
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Quaternary
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Tertiary
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middle Tertiary (3)
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Neogene
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upper Miocene (1)
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Pliocene (1)
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Paleogene
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Eocene
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Oligocene
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upper Cenozoic (1)
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Deep Sea Drilling Project
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IPOD
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deformation (4)
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igneous rocks
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porphyry (2)
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volcanic rocks
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basalts
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mid-ocean ridge basalts (1)
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tholeiitic basalt (1)
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Integrated Ocean Drilling Program (1)
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Invertebrata
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isotopes
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Pb-208/Pb-204 (1)
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stable isotopes
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O-18/O-16 (2)
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metal ores
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hafnium
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samarium
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Sm-147/Nd-144 (1)
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metamorphic rocks
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gneisses
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orthogneiss (1)
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Sonora Mexico (9)
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mineral deposits, genesis (12)
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North America
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ocean floors (2)
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North Pacific
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Tamayo fracture zone (2)
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Northwest Pacific
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Izu-Bonin Arc (1)
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West Pacific
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Northwest Pacific
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Izu-Bonin Arc (1)
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Pacific region
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GeoRef Categories
Era and Period
Epoch and Age
Date
Availability
Petrogenesis of voluminous silicic magmas in the Sierra Madre Occidental large igneous province, Mexican Cordillera: Insights from zircon and Hf-O isotopes Open Access
Mid-ocean-ridge rhyolite (MORR) eruptions on the East Pacific Rise lack the fizz to pop Open Access
Geochemical and isotopic study of Mesozoic magmatism in the Sonobari Complex, western Mexico: Implications for the tectonic evolution of southwestern North America Open Access
Slab-rollback ignimbrite flareups in the southern Great Basin and other Cenozoic American arcs: A distinct style of arc volcanism Open Access
Formation of continental fragments: The Tamayo Bank, Gulf of California, Mexico Available to Purchase
Late Oligocene to Middle Miocene rifting and synextensional magmatism in the southwestern Sierra Madre Occidental, Mexico: The beginning of the Gulf of California rift Open Access
Large igneous provinces and silicic large igneous provinces: Progress in our understanding over the last 25 years Free
Timing of intense magmatic episodes in the northern and central Sierra Madre Occidental, western Mexico Open Access
Middle Miocene to early Pliocene oblique extension in the southern Gulf of California Open Access
HISTORY OF FIELD OBSERVATIONS ON VOLCANIC ROCKS OF WESTERN MEXICO, PRE-COLUMBIAN TO RECENT Available to Purchase
Circum-Pacific arc flare-ups and global cooling near the Eocene-Oligocene boundary Available to Purchase
Ridge-trench interactions and the Neogene tectonic evolution of the Magdalena shelf and southern Gulf of California: Insights from detrital zircon U-Pb ages from the Magdalena fan and adjacent areas Available to Purchase
Epithermal deposits in México—Update of current knowledge, and an empirical reclassification Available to Purchase
Epithermal ore deposits have traditionally been the most economically important in México, with renowned world-class deposits like those in the Pachuca–Real del Monte, Guanajuato, Fresnillo, Taxco, Tayoltita, and Zacatecas districts. Whereas in certain areas (like the Great Basin in Nevada) intermediate and low sulfidation deposits have been found to be mutually exclusive in time and space; in the case of epi thermal deposits in México, the intermediate and low sulfidation types do not appear to be mutually exclusive and, to the contrary, they coexist in the same regions, formed during the same time spans, and even occur together within a single deposit. These deposits are all Tertiary in age, ranging from middle Eocene to early Miocene, with the possible sole exception of a Paleocene deposit. Their space and time distribution follows the evolution of the continental arc volcanism of the Sierra Madre Occidental and Sierra Madre del Sur. The vast majority of epithermal deposits in México belong to the intermediate (IS) or low (LS) sulfidation types; only a few high sulfidation (HS) deposits have been described in the NW part of the country (e.g., El Sauzal, Mulatos, Santo Niño, La Caridad Antigua, all of them in Sonora and Chihuahua). Because most epithermal deposits in México exhibit composite characteristics of both IS and LS mineralization styles (as well as scarce characteristics of HS), they cannot be simply characterized as IS (polymetallic deposits associated with the most saline brines) or LS deposits (mainly Ag and Au deposits associated with lower salinity brines). Thus, in this paper we propose to use an empirical classification for IS + LS deposits (that is, alkaline/neutral epithermal deposits) into three types of mineralization; namely, A, B, and C. Type A (or IS type) comprises those deposits that generally formed at greater depths from highly saline but unsaturated brines and contain exclusively from top to bottom IS styles of mineralization with a consistent poly-metallic character. Type B (or LS-IS type) comprises those deposits that exhibit dominant LS characteristics but have polymetallic IS roots (Zn-Pb-Cu); this is the most widespread type of epithermal mineralization in México. Types A and B generally exhibit mineralogic and/or fluid inclusion evidence for boiling. Type C (or LS type) comprises those deposits that exhibit only LS styles of mineralization, formed generally by shallow boiling of low salinity fluids, and have relatively high precious metal and low base metal contents. In this paper, we also review other known or attributable aspects of Mexican epithermal deposits, including ore and gangue mineralogy and their evolution in time and space, structure, geothermometry, stable iso topic composition of mineralizing fluids and other components of the deposits, chemistry and sources for mineralizing fluids, and the plausible mechanisms for the mobilization of deep fluid reservoirs and for mineral deposition in the epithermal environment.
Magmatism and tectonics of the Sierra Madre Occidental and its relation with the evolution of the western margin of North America Available to Purchase
The Sierra Madre Occidental is the result of Cretaceous-Cenozoic magmatic and tectonic episodes related to the subduction of the Farallon plate beneath North America and to the opening of the Gulf of California. The stratigraphy of the Sierra Madre Occidental consists of five main igneous complexes: (1) Late Cretaceous to Paleocene plutonic and volcanic rocks; (2) Eocene andesites and lesser rhyolites, traditionally grouped into the so-called Lower Volcanic Complex; (3) silicic ignimbrites mainly emplaced during two pulses in the Oligocene (ca. 32–28 Ma) and Early Miocene (ca. 24–20 Ma), and grouped into the “Upper Volcanic Supergroup”; (4) transitional basaltic-andesitic lavas that erupted toward the end of, and after, each ignimbrite pulse, which have been correlated with the Southern Cordillera Basaltic Andesite Province of the southwestern United States; and (5) postsubduction volcanism consisting of alkaline basalts and ignimbrites emplaced in the Late Miocene, Pliocene, and Pleistocene, directly related to the separation of Baja California from the Mexican mainland. The products of all these magmatic episodes, partially overlapping in space and time, cover a poorly exposed, heterogeneous basement with Precambrian to Paleozoic ages in the northern part (Sonora and Chihuahua) and Mesozoic ages beneath the rest of the Sierra Madre Occidental. The oldest intrusive rocks of the Lower Volcanic Complex (ca. 101 to ca. 89 Ma) in Sinaloa, and Maastrichtian volcanics of the Lower Volcanic Complex in central Chihuahua, were affected by moderate contractile deformation during the Laramide orogeny. In the final stages of this deformation cycle, during the Paleocene and Early Eocene, ∼E-W to ENE-WSW–trending extensional structures formed within the Lower Volcanic Complex, along which the world-class porphyry copper deposits of the Sierra Madre Occidental were emplaced. Extensional tectonics began as early as the Oligocene along the entire eastern half of the Sierra Madre Occidental, forming grabens bounded by high-angle normal faults, which have traditionally been referred to as the southern (or Mexican) Basin and Range Province. In the Early to Middle Miocene, extension migrated westward. In northern Sonora, the deformation was sufficiently intense to exhume lower crustal rocks, whereas in the rest of the Sierra Madre Occidental, crustal extension did not exceed 20%. By the Late Miocene, extension became focused in the westernmost part of the Sierra Madre Occidental, adjacent to the Gulf of California, where NNW-striking normal fault systems produced both ENE and WSW tilt domains separated by transverse accommodation zones. It is worth noting that most of the extension occurred when subduction of the Farallon plate was still active off Baja California. Geochemical data show that the Sierra Madre Occidental rocks form a typical calcalkaline rhyolite suite with intermediate to high K and relatively low Fe contents. Late Eocene to Miocene volcanism is clearly bimodal, but silicic compositions are volumetrically dominant. Initial 87 Sr/ 86 Sr ratios mostly range between 0.7041 and 0.7070, and initial ϵNd values are generally intermediate between crust and mantle values (+2.3 and -3.2). Based on isotopic data of volcanic rocks and crustal xenoliths from a few sites in the Sierra Madre Occidental, contrasting models for the genesis of the silicic volcanism have been proposed. A considerable body of work led by Ken Cameron and others considered the mid-Tertiary Sierra Madre Occidental silicic magmas to have formed by fractional crystallization of mantle-derived mafic magmas with little (<15%) or no crustal involvement. In contrast, other workers have suggested the rhyolites, taken to the extreme case, could be entirely the result of partial melting of the crust in response to thermal and material input from basaltic underplating. Several lines of evidence suggest that Sierra Madre Occidental ignimbrite petrogenesis involved large-scale mixing and assimilation-fractional crystallization processes of crustal and mantle-derived melts. Geophysical data indicate that the crust in the unextended core of the northern Sierra Madre Occidental is ∼55 km thick, but thins to ∼40 km to the east. The anomalous thickness in the core of the Sierra Madre Occidental suggests that the lower crust was largely intruded by mafic magmas. In the westernmost Sierra Madre Occidental adjacent to the Gulf of California, crustal thickness is ∼25 km, implying over 100% of extension. However, structures at the surface indicate no more than ∼50% extension. The upper mantle beneath the Sierra Madre Occidental is characterized by a low-velocity anomaly, typical of the asthenosphere, which also occurs beneath the Basin and Range Province of the western United States. The review of the magmatic and tectonic history presented in this work suggests that the Sierra Madre Occidental has been strongly influenced by the Cretaceous-Cenozoic evolution of the western North America subduction system. In particular, the Oligo-Miocene Sierra Madre Occidental is viewed as a silicic large igneous province formed as the precursor to the opening of the Gulf of California during and immediately following the final stages of the subduction of the Farallon plate. The mechanism responsible for the generation of the ignimbrite pulses seems related to the removal of the Farallon plate from the base of the North American plate after the end of the Laramide orogeny. The rapid increase in the subduction angle due to slab roll-back and, possibly, the detachment of the deeper part of the subducted slab as younger and buoyant oceanic lithosphere arrived at the paleotrench, resulted in extension of the continental margin, eventually leading to direct interaction between the Pacific and North American plates.