Abstract The Late Palaeozoic evolution of the St Marys Basin, mainland Nova Scotia, preserves evidence of protracted dextral shear along an intracontinental fault zone during collisional orogenesis and the assembly of Pangaea. The St Marys Basin formed within the E-W-trending Minas Fault Zone (MFZ) along the boundary between the Avalon and Meguma terranes and contains latest Devonian-Tournaisian continental clastic rocks that are 3000–4000 m in thickness. The origin and evolution of the basin is attributed to either discrete or progressive dextral strike-slip tectonics along the MFZ between the Late Devonian and Late Carboniferous. Evidence for the Late Devonian origin of the basin is recorded along its southern flank by the fabrics of the deformed c. 370 Ma granites, the overall sedimentary facies distribution, and some syndepositional features within the clastic rocks. The most intense deformation within the basin is concentrated in a relatively narrow ENE-trending zone, in which predominantly fine-grained clastic rocks are deformed into periclinal folds and related reverse faults. The orientation of this zone relative to the MFZ is consistent with dextral shear. At least some of this deformation occurred after the deposition of the overlying Visean Windsor Group. The style of deformation along the present northern margin of the basin (the Chedabucto Fault) is also consistent with regional dextral shear. The St Marys Basin is an example of basin development and evolution adjacent to an intracontinental fault zone associated with oblique convergence during orogenesis. Its evolution provides constraints on the potential relationship between the termination of the mid-Palaeozoic Acadian orogeny, subsequent basin development, and the ongoing interactions between the Avalon and Meguma terranes, and between Laurentia and Gondwana during the assembly of Pangaea. More generally, because the relationship between fabric development and motion along intracontinental strike-slip faults in continental zones is difficult to interpret, the sedimentology and structural geology in basins developed along these fault zones may preserve a less ambiguous record of the main tectonic events.

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.