Abstract This study presents a regional structural analysis and a stratigraphic study in Hidalgo and Querétaro states, east-central Mexico, where strata of the Sierra Madre Oriental foreland fold-and-thrust belt are structurally juxtaposed against Middle (?) and Upper Jurassic back-arc sequences. Rocks of the San Juan de la Rosa Formation were apparently affected by major compressive deformation during the Early Cretaceous (Nevadian?) and Laramide orogenies. Toward the east, the style of deformation is that of a typical foreland fold-and-thrust belt, whose major thrust faults are located at the Zimapán Basin margins flanked by the El Doctor and Valles-San Luis Potosí carbonate platforms. Below the El Doctor thrust, at least seven thrust faults are exposed that crosscut the middle Cretaceous rocks and the enveloping Upper Jurassic-Lower Cretaceous and Upper Cretaceous marly shaly beds in the form of a duplex. The style of deformation between the two carbonate platforms is probably thin-skinned. Speculative, semibalanced cross sections indicate an average shortening between the Zimapán Basin margins of 39.4% of its initial width. Depth to the sole thrust is estimated to be about 2000 m below the present sea level.

Abstract Despite the fact that most fold–thrust belts around the world share many features, successfully explained by the critical wedge model, the details of their geometric evolution and tectonic style development are poorly understood. In the classic section of the southern Canadian Rocky Mountains the dominant tectonic style consists of imbricate thrust sheets with relatively little internal deformation of the individual slices. In the Mexican fold–thrust Belt (Central Mexico), the age of deformation, the overall structural pattern and the total amount of shortening are similar, but the individual thrust sheets exhibit much more internal deformation as manifest by metre-scale buckle folds. One of the differences between these localities is the lateral variation of facies resulting in massive platform limestone separated by thinly-bedded basinal limestone in the Central Mexico section. Strain is concentrated toward the margins between platforms and basins. In Canada, thick platform carbonates form continuous resistant units across the Front Range. Possible reasons for the differences in tectonic style between the two sections include the dominant lithology, distribution of lithologies, taper angle of the tectonic wedges, amount of friction along the basal detachment and the degree of anisotropy of the basin facies rocks.

Abstract Mexico is widely known to be a richly endowed country in both metallic and industrial mineral deposits, the exploitation of which has constituted an economic activity of paramount importance for centuries. This paper presents an analysis of the time and space distribution of over 200 mineral deposits, which is based on the available absolute and relative ages of mineralization and constitutes a modified and updated version of the analysis of Camprubí (2009). Pre-Jurassic ore deposits are relatively scarce and of subordinate economic significance. These include Ti-bearing anorthosites and rare element pegmatites in intracratonic environments, barite sedimentary-exhalative (sedex) deposits, and ultramafic-mafic Cr-Cu-Ni(-platinum group element [PGE]) deposits in oceanic environments. Since the Jurassic, the metallogenic evolution of Mexico can be understood as a product of the evolution of two major regions: the Pacific margin and the Gulf of Mexico. The Mesozoic evolution of the Pacific margin is characterized by rifting and separation of the Guerrero composite terrane from the North American continent and the initiation of arc magmatism in an extensional continental margin setting. The ore deposits emplaced in this period are mostly polymetallic volcanogenic massive sulfide (VMS) and Cr-Cu-Ni(-PGE) deposits associated with ultramafic-mafic complexes. These occur dominantly near the boundaries of the Guerrero composite terrane. Porphyry-type deposits emplaced in the mid- Cretaceous are subordinate and, apparently, small. These likely formed in island arcs that were later accreted to the mainland. A shift from extensional to compressional tectonics resulted in the accretion of the Pacific terranes, most importantly the Guerrero composite terrane, to the Mexican mainland by the Late Cretaceous. This tectonic shift gave rise to the initial stages of the Paleocene boom in porphyry-type and sulfide skarn deposits. The continental arcs in these epochs represent the earliest stages for the Sierra Madre Occidental silicic large igneous province. The earliest known examples of epithermal deposits in Mexico are Paleocene and include, besides intermediate to low sulfidation deposits, the La Caridad Antigua high sulfidation deposit, in association with the giant La Caridad porphyry copper deposit. The Late Cretaceous iron oxide copper-gold (IOCG) deposits formed in northern Baja California and along the Pacific margin in southwestern and southern Mexico, and continued forming in the latter regions into the Paleocene. Contrastingly, some Late Cretaceous IOCG deposits formed several hundreds of km inland in northwestern Mexico, and are suspected cases for emplacement in back-arc environments. The formation of orogenic Au deposits began in the Late Cretaceous, and they kept forming into the Eocene as compressional tectonics progressed. The formation of porphyry-type, sulfide skarn, and epithermal deposits continued during the Eocene, and followed the eastward progression of the magmatism of the Sierra Madre Occidental. The number of known examples of epithermal deposits relative to porphyry-type and sulfide skarn deposits increases with time. The formation of IOCG deposits along the Pacific margin seemingly dwindled during the Eocene, although they began to form close to the Chihuahua-Coahuila border, possibly in association with the earliest stages of mineralization in the Eastern Mexican alkaline province. Also, a group of U-Au vein deposits in Chihuahua, in association with felsic volcanic rocks, is apparently restricted to the Eocene. The maximum geographic extension and climactic events of the Sierra Madre Occidental (for both magmatic and ore-forming events) were attained during the Oligocene, as the arc kept migrating eastward and southward. As magmatism reached the Mesa Central, epithermal and subepithermal, sulfide skarn, Sn veins associated with F-rich rhyolites, IOCG, and Sn-W greisen deposits formed around the main reactivated fault zones, generating the highest concentration of ore deposits known in Mexico. The focus of magmatism and mineralizing processes shifted progressively southward in the Eastern Mexican alkaline province between the Oligocene and the Miocene, and intensified significantly in northern Coahuila and Chihuahua in the Oligocene. This province also includes alkaline porphyry Cu-Mo deposits, REE-bearing carbonatites, and polymetallic skarns. During the Miocene, the magmatism of the Sierra Madre Occidental retracted dramatically southward and began concentrating in an E-W arrangement that corresponds to the Trans-Mexican volcanic belt, while continental extension evolved into the opening of the Gulf of California. During this time, metallogenic processes associated with the Sierra Madre Occidental virtually ceased. From the late Miocene, the formation of epithermal deposits, sulfide skarns, and porphyry-type deposits resumed in the Trans-Mexican volcanic belt and the Eastern Mexican alkaline province, whereas IOCG deposits seem restricted to the latter. The opening of the Gulf of California represents the beginning of a new cycle in metallogenesis, with the formation of shallow analogues of sedex deposits and sedimentary phosphorites along the Baja California peninsula, epithermal deposits near the cul-de-sac of the Gulf, and recent VMS deposits in passive continental margins and mid-ocean ridges. The sedimentary-diagenetic history of the Gulf of Mexico includes the formation of Mississippi Valley-type (MVT) and associated industrial mineral, red bed-hosted U and Cu-Co-Ni, sedimentary phosphorite, and sedex deposits. The emplacement of MVT and red bed-hosted deposits was associated with the emplacement of basinal brines through reactivated faults that controlled basin inversion. These faults also played a significant role as channelways for magmas and associated magmatic-hydrothermal ore deposits of the Eastern Mexican alkaline province.

ABSTRACT Two main tectonic scenarios have been proposed for the area corresponding to the Guerrero terrane in western Mexico. The first model suggests that the Guerrero terrane was an allochthonous volcanic arc developed over oceanic substrate, which was accreted to nuclear Mexico. The second tectonic model proposes that the Guerrero terrane was a para-autochthonous volcanic arc developed over continental crust, which was rifted during the extensional phase of the Arperos back-arc basin and then tectonically attached to nuclear Mexico. Based on U-Pb geochronology and Hf isotope analyses of detrital zircon grains extracted from Mesozoic sedimentary successions of the Guerrero terrane and western nuclear Mexico, this study provides new evidence to support the interpretation that the Late Jurassic–Early Cretaceous Guerrero terrane was built above a pre–Late Jurassic continentally sourced basement. Hf isotopic signatures of detrital zircon from Late Jurassic–Early Cretaceous sedimentary rocks of the Guerrero terrane range from –14 to +13 and display depleted mantle model ages (T DMc , using a mean crustal value of 176 Lu/ 177 Hf = 0.015) between ca. 2.0 and 0.3 Ga, indicating provenance from both pre–Late Jurassic basement and juvenile crustal components. The most juvenile magmas were formed during the earliest Cretaceous extensional phase, which resulted in the formation of the Arperos basin. Additionally, the negative ε Hf ( t ) values are consistent with recycling of Proterozoic and Paleozoic continental materials in Mesozoic magmas.

Abstract The southwestern North America porphyry copper province comprises adjacent parts of the U.S. states of Arizona, New Mexico, and Texas, and the Mexican states of Sonora, Chihuahua, northern Sinaloa, and Baja California. The province has an estimated total endowment (production + reserves + resources) of 295 million tonnes of copper metal, 96% of which is in deposits of Laramide (∼80–45 Ma) age. This is one of the major accumulations of the element known in the Earth's crust. In addition to having played a major historical role with regard to the discovery, development, mining, and scientific study of porphyry copper deposits, large remaining reserves and resources assure that the this porphyry province will continue to be a factor in world copper supply for many years to come. The southwestern North America province is largely underlain by mid-Proterozoic continental crust covered by upper Proterozoic to mid-Paleozoic miogeoclinal sedimentary rocks. Arc magmatism commenced in the area in the Triassic and continued until extinguished by ridge subduction that started in early Miocene time; this resulted in its conversion from a convergent to a transform margin. A long-lived series of NW-trending sedimentary basins evolved parallel to the arc from Jurassic through mid-Cretaceous time. The Laramide porphyry deposits were emplaced during a continental-scale episode of flat subduction and strong compression. This was accompanied by metaluminous to weakly peraluminous calc-alkaline I-type magmatism. Hypogene porphyry copper mineralization is dominated by chalcopyrite (± bornite), accompanied by K-silicate, transitional K-silicate-sericitic, and sericitic alteration. Subsequent to porphyry emplacement, much of the region was subjected to an episode of weathering and erosion, followed in the mid-Tertiary by a switchover to an extensional tectonic regime and the eruption of silicic volcanic rocks that blanketed much of the region. Two episodes of weathering-related oxidation, leaching, and enrichment, one prior to mid-Tertiary volcanisim (Eocene-Oligocene) and the second of Miocene age, produced rich supergene copper ores that were the mainstay of production in the province through the 1970s. Southwestern North America Laramide porphyry copper deposits are very near the median of worldwide porphyry deposit distributions in regard to size, contained Cu metal, median Cu grade, and median Mo grade. Median Au grades are significantly lower than the global median. The depth of erosion of pre-Laramide arcs in southwestern North America probably accounts for the relative paucity of porphyry deposits, and there are segments of the Laramide arc that have been tectonically denuded during mid-Tertiary extension, also resulting in a lack of deposits. There are, however, segments of the Laramide arc with similar, apparently appropriate, levels of erosion and preservation that have widely different deposit densities and/or copper endowment that is as yet unexplained. The apparent lack of Eocene to Oligocene porphyry deposits is also difficult to account for; hypabyssal rocks of this age are quite common and copper-bearing polymetallic skarn and high-temperature replacement and vein deposits are locally associated with them, but there is only one small, low-grade porphyry deposit of this age documented in southwestern North America. Although the region has been heavily explored for exposed porphyry copper deposits, there remain excellent opportunities for discovery, given that an estimated 54% of the porphyry trend is covered by post-Laramide rocks or unconsolidated sediments. Exploration targets include undrilled or poorly drilled extensions of known deposits—both laterally and, especially, at depth; deposits or dismembered parts of deposits under structural cover in areas of post-Laramide extension; and deposits under postore volcanic and alluvial cover. Future production will increasingly be dominated by open pit low-grade and underground high-grade hypogene milling ores, with an important molybdenum by-product credit.