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This study presents U-Pb zircon ages and Lu-Hf zircon isotope data for Cretaceous-Paleocene plutonic rocks along a W-E transect in northwestern Mexico. These data are combined with tectonic reconstruction that restores Late Cenozoic extensional deformation and shows the position of magmatism at 36 Ma. Zircon U-Pb ages results span from 142 to 58 Ma and demonstrate that the continental arc migrated northeastward at 1–2.5 km/Myr. These rates are slower than previously interpreted, but consistent with landward arc migration rates observed in the Andes. Weighted mean initial epsilon hafnium (εHf(t)) values of plutonic rocks along the transect range from + 8.8 to −9.1. The heterogeneity in the zircon εHf(t) is spatially related to the pre-Cretaceous basement provinces that the intrusive rocks were emplaced into. Zircon εHf(t) values of western Baja California display positive values ranging from + 8.8 to + 2.6 suggesting they were formed from a moderately depleted mantle and were emplaced into the Guerrero-Alisitos-Vizcaino terrane. Zircon εHf(t) values in the eastern part of Baja California and most of Sonora are heterogeneous ranging between −0.7 and −9.1 and may be formed from a relatively slightly more evolved mantle source and end up more evolved after crustal assimilation of metasediments. Zircon εHf(t) values ranging from + 8.7 to + 2.9 in Chihuahua are consistent with a depleted-mantle derived melt and assimilation of Grenville lithospheric province. Our results highlight how Hf isotopic signatures help to constrain the pre-Cretaceous basement configuration in northwestern Mexico despite the few exposed outcrops along the transect. [ABSTRACT FROM AUTHOR]

The Santa María and Antares Zn-Pb(-Ag) skarn deposits in the Velardeña Mining District are located in central–NW Mexico. They lie 470 m apart along the contact between Oligocene felsic intrusions and Cretaceous limestones, and were developed during prograde, retrograde, post-ore (Santa María), and late stages. Firstly, the prograde stage was formed by fluids at ~ 600 °C and 15 wt% NaCl equiv., and consists of garnet + wollastonite ± clinopyroxene and biotite ± K-feldspar assemblages. Secondly, the retrograde/ore stage was formed by fluids at 300–500 °C with salinities of 20–30 wt% CaCl2 (Santa María) and > 40 wt% NaCl equiv. (Antares). It comprises assemblages of chlorite, amphibole, epidote, calcite, scapolite, quartz, sericite, adularia, fluorite, and muscovite associated with sphalerite, pyrite, galena, pyrrhotite, arsenopyrite, chalcopyrite, and Pb-Bi-Sb sulfosalts. Thirdly, the post-ore stage was formed by fluids at ~ 400 °C and 20–30 wt.% CaCl2 and comprises poorly mineralized calcite veins. Fourthly, the late stage was formed by fluids at < 300 °C and 20–30 wt.% CaCl2 (Santa María) and ~ 15 wt% NaCl equiv. (Antares), and crystallized tetrahedrite-group minerals and pyrite + marcasite. δ18Ofluid between ~ 14‰ and 23‰ at Santa María and between ~ 12‰ and 17‰ at Antares show a less-modified magmatic affinity for mineralizing fluids at Antares; δ13Cfluid between 0‰ and –6‰ register recycling of sedimentary C. Moreover, sulfides with δ34SVCDT between –3‰ and 2‰ reveal a magmatic source for S. Altogether, these data suggest that, at Santa María, magmatic-derived fluids actively interacted with the wall rocks, whereas at Antares the fluid-rock interaction was milder. In both deposits, metal deposition was triggered by the cooling and neutralization of ore-bearing fluids with carbonate rocks. Our 40Ar/39Ar dates for adularia of ca. 37.5 Ma place the deposits within the Eocene–early Miocene metallogenetic epoch of central–NW Mexico, during which other world-class skarn-epithermal systems were emplaced (e.g., Concepción del Oro and Mazapil-Peñasquito). [ABSTRACT FROM AUTHOR]

Hereditary cancer syndromes (HCS) are genetic diseases with an increased risk of developing cancer. This research describes the implementation of a cancer prevention model, genetic counseling, and germline variants testing in an oncologic center in Mexico. A total of 315 patients received genetic counseling, genetic testing was offered, and 205 individuals were tested for HCS. In 6 years, 131 (63.90%) probands and 74 (36.09%) relatives were tested. Among the probands, we found that 85 (63.9%) had at least one germline variant. We identified founder mutations in BRCA1 and a novel variant in APC that led to the creation of an in-house detection process for the whole family. The most frequent syndrome was hereditary breast and ovarian cancer syndrome (HBOC) (41 cases with BRCA1 germline variants in most of the cases), followed by eight cases of hereditary non-polyposic cancer syndrome (HNPCC or Lynch syndrome) (with MLH1 as the primarily responsible gene), and other high cancer risk syndromes. Genetic counseling in HCS is still a global challenge. Multigene panels are an essential tool to detect the variants frequency. Our program has a high detection rate of probands with HCS and pathogenic variants (40%), compared with other reports that detect 10% in other populations. [ABSTRACT FROM AUTHOR]

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The Caborca orogenic gold belt is a large gold metallogenic province located in the North American Cordillera that hosts orogenic gold-bearing quartz veins and extends from northwestern Mexico into the southwestern United States. The Caborca orogenic gold belt includes a number of deposits currently in production (e.g., La Herradura, San Francisco-Llano, El Chanate, Soledad-Dipolos, and Noche Buena) that, combined, contain gold reserves and resources of over 10 million ounces. Extensive new 40Ar/39Ar geochronology of white micas associated with gold-bearing quartz veins along the Caborca orogenic gold belt suggests that mineralization developed rapidly after -69 Ma, peaked at ~61 Ma, and decreased more slowly from 58 to 36 Ma, when it ceased. Triggering of mineralization is closely related to an increase in the rate of convergence and the subsequent shallowing of the subducted Farallon slab, which resulted in rapid eastward migration of the magmatic arc toward the continent during the Late Cretaceous- Eocene Laramide orogeny. Mineralization within the Caborca orogenic gold belt formed contemporaneously with some other orogenic gold deposits along the North American Cordillera, including districts in Alaska (e.g., Chichagof, Juneau, and Port Wells) and Canada (e.g., Bridge River). After a process of crustal shortening/thickening during the early compressive stage (-90-70 Ma) of the Laramide orogeny, which was also a time for generation of mineralizing fluids, a process of synconvergent crustal extension started at -70 Ma and affected the Cordillera forearc region in northwestern Mexico as a response to the flat subduction and the eastward Laramide arc migration. This Laramide synconvergent extension produced a marked cooling of the thinned crust, which, in turn, generated regional brittle conditions that facilitated the ascent and precipitation of metal-laden metamorphic fluids that formed the quartz-gold vein mineralization along the Caborca orogenic gold belt. Another consequence of the eastward arc migration during the Laramide orogeny was the generation of contemporaneous Late Cretaceous-Eocene Cu-Mo porphyry deposits in northwestern Mexico and the southwestern United States. In this scenario, orogenic gold deposits would have formed in the amagmatic forearc region, whereas the porphyries would have been generated farther to the east in the magmatic arc region. In this mineralization model, we interpret that the Caborca orogenic gold belt area was more uplifted and suffered higher degrees of denudation (veins formed at depths of ~4-6 km) than the region of Cu-Mo porphyries that formed at shallower crustal depths (~1-2 km). In other words, both coeval mineral belts were exposed next to each other, even though they represent very different crustal levels. This crustal level disparity could be explained by a period of intense Eocene to Oligocene tectonic/crustal denudation that preferentially affected the previously overthickened forearc region. Perhaps due to isostatic rebound, at least 4 to 6 km of crustal material from the forearc region was removed until the final exhumation of the Caborca orogenic gold belt veins occurred, most likely by the Oligocene. Soon after this period of intense crustal denudation, Oligocene-Miocene epithermal mineralization overprinted both the Caborca orogenic gold belt and the porphyry Cu-Mo belt. In addition, supergene alteration of hypogene orogenic mineralization and supergene enrichment of the porphyry deposits (enriched layers of secondary copper minerals) increased mineral concentrations due to groundwater level fluctuations (oxidationreduction cycles) in an arid desert environment that prevailed since the Miocene. The combination of all these tectonic and climatic factors makes northwestern Mexico a unique and attractive place in the North American Cordillera to undertake mineral exploration endeavors. [ABSTRACT FROM AUTHOR]

Copyright of Boletín de la Sociedad Geológica Mexicana is the property of Sociedad Geologica Mexicana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A geochemical mass balance study, combined with petrography, bivariate Au and Ag geochemical analysis, and inclusion study in pyrites and native gold, was performed on a suite of hydrothermally altered host rocks and contemporaneous quartz veins from the Caborca Orogenic Gold Belt in NW Sonora, Mexico (COOC; by its abbreviations in Spanish: Cinturón de Oro Orogénico Caborca). These combined studies helped evaluating the geochemical homogeneity of the mineralizing fluids that formed the alteration envelopes and the auriferous quartz veins in the entire area occupying the COOC (∼400 km long and ∼60-80 km wide belt). The isocon statistical technique used in the mass balance study was applied on 20 pairs of mayor and trace element geochemical data of altered and fresh rock samples. The results show that the majority (>50 %) of the altered host rocks are enriched in K2O, W, Cu, Pb, Mo, Tl, Be, Zn, V, Sb, Ag, Sn, SiO2, Se, Ni and FeO, and are clearly depleted in Ca, Y, Na, Ho, Co, Sr, Yb, Mn, Dy, Er and Tb. The similar pattern of enrichment and depletion was shown by most of the studied samples suggesting a high degree of geochemical homogeneity of the mineralizing fluids. Petrography on both the altered and fresh rocks indicates that the hydrothermal alteration primarily consisted of silicification, sericitization, chloritization, epidotization and pyritization. The bivariate Au and Ag geochemical studies, done in auriferous quartz veins, show a strong positive correlation between these two elements and the enriched elements shown by the mass balance study on the altered host rocks. Therefore, these elements could be utilized as a geochemical exploration guide to targeting orogenic gold deposits in the region. Multiple inclusions of native gold and silver, galena, covellite, sphalerite, molybdenite, scheelite and tourmaline were encapsulated in pyrite and native gold grains in the quartz veins. Presence of these mineral occurrences explains most of the elemental anomalies obtained geochemically on the quartz veins and altered host rocks. In conclusion, the geochemical homogeneity of the mineralizing fluid, proposed in this study, implies that the mineralization (Aurich quartz veins) and associated alteration assemblages were part of a large-scale event synchronous with the Laramide orogeny when compressional tectonism was active during Late Cretaceous to Early Tertiary time. [ABSTRACT FROM AUTHOR]

A semi-quantitative thermochronological study, combining U-Pb and 40Ar/39Ar geochronology, has allowed assessment of the crystallization and cooling history of the Laramide Sierrita Blanca granite as well as the thermal effects resulting from the intrusion into the Mesoproterozoic host rocks (~1.1 Ga Murrieta granite). The U-Pb zircon age discrepancy between two samples of the Sierrita Blanca granite (72.6 ± 1.2 Ma and 69.7 ± 1.0 Ma) could be explained by a process of faster magma cooling in the contact zone with the host Murrieta granite. However, that the Sierrita Blanca granitic unit was made up of multiple intrusions of similar compositions emplaced relatively close in time cannot be discarded. The 40Ar/39Ar ages of both biotite and K-feldspar for the granite collected close to the contact are also significantly older than the ages for the sample collected in a more internal zone of the intrusion. The initial cooling of the Sierrita Blanca granite was fairly fast and monotonous from the closure temperature of zircon to that of biotite (~36-32°C/Ma). Subsequently, the cooling of these Laramide rocks became relatively slow (~10-9°C/Ma) between the closure temperature of biotite and K-feldspar. These estimated cooling rates are similar, perhaps slightly slower, to the ones estimated for other Laramide granitoids in NW Mexico. Three samples of the host Murrieta granite, collected at different distances from the Laramide intrusion, were dated by U-Pb zircon geochronology at ~1.1 Ga, reiterating that the U-Pb zircon systematics are quite resistant to thermal effects inflicted by intrusions like the one in the Sierrita Blanca. However, close inspection of the U-Pb zircon data suggests the presence of Pb loss for some of the zircons. This Pb-loss phenomenon is most pronounced in the zircons from the sample collected at the contact with the Sierrita Blanca intrusive where heat and/or hydrothermal fluids are released by the Laramide intrusion. It is important to note that away from the intrusion-host contact there is a gradual decrease of such thermal effects in the rocks until samples with zircons that show no effects of resetting as suggested by their total U-Pb zircon concordance. This thermal resetting is more prominent in the 40Ar/39Ar systematics of biotite and K-feldspar, since they are totally reset to Laramide ages, including the sample collected the farthest away from the contact. The estimation of post-resetting cooling of biotite and K-feldspar from the host rocks at ~18-15°C/Ma is, in a sense, coherent with the cooling estimates for the same minerals for the Sierrita Blanca granite. This suggests that the general cooling of the Sierrita Blanca after the Laramide intrusion was, for the most part, coherent for the entire area and ended, as expected, in the more internal zones of the Laramide intrusion. Lastly, it is important to point out that the Miocene magmatic pulse present in the Sierrita Blanca and adjacent areas has not caused any thermal disturbance to the Cretaceous or Mesoproterozoic igneous rocks studied in the area. [ABSTRACT FROM AUTHOR]

The Zona Canteras-Puerto Peñasco area, previously known as Seven Hills, is located ~20 km ENE of the town of Puerto Peñasco in NW Sonora, Mexico. Crystalline basement in this area is key to defining Proterozoic provinces of SW Laurentia and has important implications for Phanerozoic tectonics and formation of the active continental margin of North America. New U-Pb zircon ages (LA-MC-ICPMS) of two banded gneisses in this area yield 207Pb/206Pb ages at 1764 ± 3 Ma and 1725 ± 3 Ma. Zircons from both samples are well-behaved in the U-Pb systematics and present age and compositional homogeneity, suggesting that these rocks are Paleoproterozoic orthogneisses. These crystallization ages combined with whole rock major- and trace-element geochemistry and Sm-Nd in whole rock and Lu-Hf isotopic determinations on zircons by laser ablation suggest that the banded gneisses have affinities with rocks of the Yavapai province as defined in the Quitovac area ~45 km to the east and in the region of Gunnison-Salida, Colorado, USA. Both samples plot in the volcanic arc environment of granite formation (Y vs Nb discrimination diagram) and have epsilon Hf (initial) values between +1.85 and +5.05 with corresponding single-stage Hf model ages (TDM) at 1.98-2.07 Ga and two-stage Hf model ages (TDMC) at 2.07-2.50 Ga. Sm-Nd whole rock isotopic analyses from three Paleoproterozoic gneisses have epsilon Nd (initial) values between +1.86 and -0.57 with corresponding Nd model ages (TDM) at 1.91-2.02 Ga. The magmatic protoliths of these gneisses could have been formed mostly from mantle sources with some degree of crustal contribution, which is similar to rocks from the Yavapai province in SW North America. This petrogenesis contrasts with typical Mojave-province rocks that are characterized by significantly greater crustal contamination (as much as 30-40% in Death Valley). If these Mojave province rocks exist in NW Sonora they must be located to the west of the Zona Canteras-Puerto Peñasco area. [ABSTRACT FROM AUTHOR]

Abstract: Hornblende step-heating 40Ar/39Ar dating for granitic plutons along an E–W transect of central Sonora was carried out to constrain the Late Cretaceous–early Tertiary migration of the cordilleran magmatic arc across northwestern Mexico. Geochronological data from previous studies offer a good estimate of the overall process, but because they come from different dating schemes performed on a variety of rocks and/or minerals with a wide range of closure temperatures, the ages largely overlap when plotted on a map. Previous data suggest that the Cordilleran magmatic arc was nearly static in the western portion of the Peninsular Ranges batholith in Baja California (140–105Ma), then the axis of magmatism migrated east at approximately 10km/Ma and reached coastal Sonora approximately 90Ma ago. The locus of the plutonic emplacement continued to migrate inland during the Laramide magmatic pulse (80–40Ma), penetrating up to central Chihuahua. New argon data indicate that granitic plutons intruded the region northeast of Bahía Kino, in coastal Sonora, approximately 77Ma ago. Magmatism subsequently moved east to the area surrounding the city of Hermosillo approximately 69Ma ago and continued its easterly migration, reaching the Sonora–Chihuahua state boundary 59Ma ago. However, the granitic rocks of east-central Sonora yield ages in a relatively wide range of 62–56Ma. Synchronic plutons reported farther east in central Chihuahua suggest an unusually broad magmatic arc, which appears difficult to explain on the basis of the traditional subduction model assumed for southwestern North America during this time and may reflect particular – and little understood – tectonic conditions derived from the relatively flat subduction regime prior to the extinction of the Laramide magmatic arc. Moreover, volcanic rocks exposed in east-central Sonora yield fairly old U–Pb zircon dates of 90–70Ma, which have no known contemporaneous plutons, and complicate the scenario for the Laramide event in Sonora, perhaps requiring the existence of a second volcanic arc. Considering solely the evidence from granitic plutons, the data provide a systematic way to evaluate the shift of magmatic activity across Sonora. It needs a proper restitution for the conspicuous Cenozoic extension affecting the region. After restoring the cumulative extension of 90% estimated for east-central Sonora, a rate of approximately 8.5km/Ma of eastward migration can be roughly estimated for the Laramide arc across Sonora. [Copyright &y& Elsevier]

The El Barqueño epithermal vein district is located in the southwestern part of the Sierra Madre Occidental of Mexico. It is made up of several polymetallic (Au-Ag-Cu-Zn-Pb) epithermal veins hosted by a volcanoplutonic assemblage of andesitic rock s, granites, and granodiorites, which belong to the Lower Volcanic Supergroup of the Sierra Madre Occidental, within the Jalisco block. The veins trend from 45° to 100°, dipping to the southeast and south, and steepening with depth. The maximum strike length of the veins at El Barqueño is about 5 kin, and the maximum vein thickness is about 10 m (avg 2-3 m), narrowing with depth. The paragenetic sequence indicates two main mineralization stages. Stage I occurs as breccias with base metal sulfides and virtually no gold or silver. Stage II consists of crustiform quartz bands that form symmetrical vein fillings and contain the precious metal mineralization. Rhombohedral adularia crystals and quartz pseudomorphs after bladed calcite ar e widespread in stage II, providing evidence for boiling. Gold- and silver-bearing metallic minerals locally precipitated directly on adularia crystals, an association indicating boiling as the main mechanism of metal deposition. Conductive cooling and m ixing also may have been important. The temperature and salinity of the mineralizing fluids ranged from 101° to 252°C and 0.2 to 19.1 wt percent NaCl equiv, respectively. Whereas temperatures cluster in the range of 120° to 160°C, salinities have a bimodal distribution, mos t of them falling below 3 or higher than 10 wt percent NaCl equiv. These two arrays of salinity values only locally reflect mixing and may represent different sources of mineralizing fluids, possibly dominated by meteoric and magmatic sources, respective ly. An adularia separate from crustiform quartz bands of stage II was dated by 40Ar/39Ar geochronology at 57.91 ± 0.44 Ma (isochron age). Thus, El Barqueño has the oldest absolute age of any epithermal deposit in Mexico an d suggests the existence of a previously unrecognized Paleocene metallogenic event in southwestern Mexico associated with several types of ore deposits, including iron oxide-copper-gold, porphyry-type skarn and epithermal deposits. This further suggests that older rocks beneath the Upper Volcanic Supergroup of the Sierra Madre Occidental may be prospects for other epithermal veins and that exploration for epithermal deposits and related mineral deposit types should be focused in the oldest outcrop porti ons of the Sierra Madre Occidental. [ABSTRACT FROM AUTHOR]

The Ixtacamaxtitlán hydrothermal deposit is made up of a succession, from bottom to top, of: (1) a porphyritic subvolcanic body, crosscut by quartz veins, and a stockwork with subordinate sulfides (pyrite and chalcopyrite), showing propylitic alteration haloes overprinting a previous potassic alteration event (biotitization); (2) an overlying, kaolinized lithic-rich rhyolitic tuff; and (3) a layered opal deposit with preserved sedimentary structures. This vertical zonation, coupled with the distribution of the alteration assemblages, lead us to the interpretation of the whole as a porphyry-type deposit grading upwards to a barren, steam-heated, acid-leached, kaolinite blanket with a partially preserved silica sinter on top. Both the fluid inclusion study carried out on the veins and stockwork, and the stable isotopic analyses of the kaolinized bodies, suggest the presence of two major hydrothermal events. The older event is characterized by the occurrence of hot hypersaline fluids (up to 320°C and 36 wt% NaCl equivalents), likely of magmatic origin, closely associated with the emplacement of the underlying early Miocene porphyry-type deposit. The later event is characterized by the presence of cooler and dilute fluids (up to 140°C and 4 wt% NaCl equivalents) and by advanced argillic alteration close to the paleosurface. The calculated isotopic composition of water in equilibrium with the kaolinitic sequence plots close to and underneath the meteoric water line, partially overlapping the Los Humeros present-day geothermal fluids. This evidence coupled with the petrographic observations suggests that steam-heated phreatic waters altered the lithic-rich rhyolitic tuff. This would have occurred when acid vapors, exsolved from deeper hydrothermal fluids by boiling, reached the local paleowater table and condensed, after a sector collapse that changed the system from lithostatic to hydrostatic conditions. [ABSTRACT FROM AUTHOR]

A detailed geochemical characterization of 19 representative Proterozoic basement rocks in the Quitovac region in northwestern Sonora, Mexico, has identified two distinct Paleoproterozoic basement blocks that coincide spatially with the previously proposed Caborca and "North America" blocks. New U-Pb zircon geochronology revises their age ranges, the Caborca (1.781.69 Ga) and "North America" (1.71-1.66 Ga) blocks at Quitovac, and precludes a simple age differentiation between them. In addition, Grenvillian-age granitoids (ca. 1.1 Ga), spatially associated with the Caborca block have been identified at Quitovac. Nd isotopes and major- and trace-element geochemistry support the distinction of these Paleoproterozoic blocks. Granitoids of the "North America" block are characterized by depleted εNd values (3.4-3.9) and younger Nd model ages (18001740 Ma) and have lower K[sub 2]O, Y, Rb, Ba, Th, REE, and Fe/Mg values than coeval rocks of the Caborca block. The Caborca block granitoids are likewise characterized by slightly less depleted εNd (0.6-2.6) and older Nd model ages (2070-1880 Ma). Despite the subtle differences, granitoids from both the Caborca and "North America" blocks exhibit island arc-like affinities. We propose that the Proterozoic basement rocks from the Quitovac region are an extension of the Proterozoic crustal provinces in the southwestern United States. Specifically, rocks of the Caborca block exhibit an affinity to rocks of either the Yavapai province or the Mojave-Yavapai transition zone, whereas rocks of the "North America" block have signatures similar to those of the Mazatzal province or possibly the Yavapai province of Arizona. The new isotopic ages and geochemical data do not support the existence of the Late Jurassic Mojave-Sonora megashear at Quitovac, as originally proposed. However, the Quitovac region accounts only for a small fraction of the Proterozoic basement in Sonora, so these findings do not eliminate the possibility of a megashear elsewhere in northern Sonora. Our new data create the possibility of alternative hypotheses for the distribution of Paleoproterozoic crustal provinces in southwestern North America that affect reconstructions of the original southwestern margin of Laurentia, and reduce uncertainties in the configuration, timing, and existence of the Proterozoic supercontinent, Rodinia. Keywords: isotopes; geochemistry; geochronology; tectonics; Proterozoic; Sonora; Mexico. [ABSTRACT FROM AUTHOR]

Background: Pathogenic variants (PVs) of BRCA genes entail a lifetime risk of developing breast cancer in 50-85% of carriers. Their prevalence in different populations has been previously reported. However, there is scarce information regarding the most common PVs of these genes in Latin-Americans. This study identified BRCA1 and BRCA2 PV frequency in a high-risk female population from Northeastern Mexico and determined the association of these mutations with the patients' clinical and pathological characteristics.Methods: Women were divided into three groups: aged ≤ 40 years at diagnosis and/or risk factors for hereditary breast cancer (n = 101), aged > 50 years with sporadic breast cancer (n = 22), and healthy women (n = 72). Their DNA was obtained from peripheral blood samples and the variants were examined by next-generation sequencing with Ion AmpliSeq BRCA1 and BRCA2 Panel using next-generation sequencing.Results: PVs were detected in 13.8% group 1 patients (BRCA1, 12 patients; BRCA2, 2 patients). Only two patients in group 2 and none in group 3 exhibited BRCA1 PVs. Variants of uncertain significance were reported in 15.8% patients (n = 16). In group 1, patients with the triple-negative subtype, PV frequency was 40% (12/30). Breast cancer prevalence in young women examined in this study was higher than that reported by the National Cancer Institute Surveillance, Epidemiology (15.5% vs. 5.5%, respectively).Conclusions: The detected BRCA1 and BRCA2 PV frequency was similar to that reported in other populations. Our results indicate that clinical data should be evaluated before genetic testing and highly recommend genetic testing in patients with the triple-negative subtype and other clinical aspects. [ABSTRACT FROM AUTHOR]

Although orogenic gold deposits in Mexico were mostly formed during the Cenozoic, they started forming during the Late Cretaceous, or perhaps even earlier. Mylonitic zones in the Oaxacan metamorphic complex span either Permo-Triassic or Triassic-Jurassic ages, but none of these have been formally associated with the existing orogenic gold occurrences. Given the current scarcity of age data for them, any interpretation concerning the age patterns or distribution of orogenic gold deposits in Mexico other than those in the Sonoran belt is hitherto deemed to be precarious. A few known Mesozoic examples are part of the Quitovac–La Choya deposits in the Caborca Orogenic Gold Belt (COGB) in Sonora, and Los Uvares in the Los Cabos Block (southernmost part of the Baja California Peninsula). The COGB constitutes the most economically important and geologically consistent mineralized area in Mexico with respect to orogenic gold deposits. Also, the COGB arguably correlates with the Mother Lode trend in California and Nevada, whereas the cluster of deposits in the Los Cabos Block may have correspondent similarly mineralized areas in mainland southwestern Mexico (Jalisco Block). Other areas with orogenic gold deposits in Mexico, which have been traditionally overlooked or scantly mentioned, are the northernmost part of the Baja California Peninsula, and the Arteaga and Oaxacan metamorphic complexes, although no geochronological data are available from these. Besides the overly lack of such data, one of the typical problems concerning the characterization and metallogenesis of orogenic deposits in Mexico has been their inaccurate or incorrect ascription to other genetic paradigms or types of deposits, such as epithermal or porphyry Cu–Au deposits, therefore misguiding exploration efforts. The formation of orogenic gold deposits in Mexico has been commonly associated with the Laramide orogeny, in association with cataclastic or mylonitic deformation and shear zones. Their depth of formation, under lithostatic pressure, has ben estimated at a range between ~ 3 and ~ 10 km. Alteration assemblages in them are generally dominated by quartz ± “sericite” ± pyrite, and may be carbonate-rich. The hypogene mineralogy of orogenic gold deposits in Mexico is normally dominated by sulfides like pyrite, galena, sphalerite and whereas gold normally occurs as “electrum”, also known as unspecified Ag-rich gold, Au-rich silver, or as free gold. The latter may either be a hypogene or supergene mineral, in which case it is likely to be due mostly to the leaching-off of Ag from “electrum”. Te-rich associations are rare and have complex parageneses that consist typically of silver and/or gold tellurides. The mineralizing fluid precipitation into quartz veins occurred at temperatures ~ 350 °C and are CO 2 -rich deeply seated crustal brines from metamorphic sources, with salinities typically ranging between ~ 2 and ~ 10 wt.% NaCl equiv. but attaining up to ~ 33 wt.% NaCl equiv. [ABSTRACT FROM AUTHOR]

A detailed petrographic, geochemical, and U Pb geochronological study of altered volcanic ash layers, collected in eight outcrops of the Late Cretaceous San Felipe Formation (Sierra Madre Oriental, Northeastern Mexico), has been carried out. The main objectives have been: (1) to establish a deposit period, and (2) to propose a reliable provenance-transport-deposit-diagenetic model. These volcano-sedimentary strata represent the altered remains of vitreous-crystalline ash (main grains: quartz + K-feldspar (sanidine) + Na-plagioclase + zircon + biotite; groundmass: glass + calcite + clinochlore + illite) deposited and preserved in a shallow, relatively large in area, open platform environment. Major and trace element geochemistry indicate that parent volcanism was mainly rhyodacitic to rhyolitic in composition. Discrimination diagrams suggest a link to continental arc transitional to extension tectonic setting. U Pb geochronology in zircon has revealed that the volcanic ash was released from their sources approximately during the range 84.6 ± 0.8 to 73.7 ± 0.3 Ma, being transported to the depocenters. Burial diagenesis process was marked by: (a) a limited recycling, (b) the partial loss of original components (mainly K-feldspar, plagioclase, biotite and glass), and (c) the addition of quartz, calcite, illite and clinochlore. The location of the source area remains uncertain, although the lack of enrichment in Zr/Sc ratio suggests that ashes were subjected to relatively fast and short-distance transport process. El Peñuelo intrusive complex, at 130–170 km west of the depocenters, is the nearest known zone of active magmatism during the Upper Cretaceous. This intermediate to felsic pluton, characterized by a geochemical affinity to post-orogenic tectonic setting, could be linked to the volcanic sources. [ABSTRACT FROM AUTHOR]

Continental rifts require focused strain to rupture and form an ocean basin. In oblique rifts, such as the Gulf of California, focused transtensional strain associated with strike-slip faulting may serve as a catalyst for rupture. To test this hypothesis, we analyzed structural mapping, geochronology, paleomagnetism, and fault kinematics of pre- and synrift rocks exposed in an ~200 km² coastal mountain belt flanking the eastern rift margin of the northern Gulf of California. This coastal Sonora region hosts the onshore portion of the transform boundary between the Upper Tiburón and Adair-Tepoca marine basins--two early-formed oblique rift segments. Extension commenced here between 11.5 Ma and 7 Ma, resulting in 25°-40° of E-NE tilting, initiation of clockwise verticalaxis rotation of fault-bounded blocks, and minor basin sedimentation. Rates of deformation prior to 7 Ma are unconstrained due to a lack of exposed syntectonic deposits. Deformation after 7 Ma was associated with rapid tilting and the majority of observed clockwise vertical-axis rotation and strikeslip faulting. Nonmarine sedimentary basins accumulated coarse sediments above an unconformity eroded across older, tilted strata. By 5-6 Ma, deformation in coastal Sonora must have largely ceased and migrated westward into the Upper Tiburón marine basin. We document up to 120% total extension and total clockwise block rotations up to 53°. In portions of the study area, extension and rotation were supplanted by strike-slip faulting as deformation proceeded. We develop a tectonic model for this Coastal Sonora fault zone, which is bounded by major NW-striking transform faults with >10 km of displacement. Internal to the Coastal Sonora fault zone, the majority of an estimated 6.2 ± 1.1 km of dextral deformation, associated with up to 5.7 km of WNW-directed extension, occurred over the final 1-2 m.y. of its life span, at a strain rate approaching 10-14 s-1. This activity occurred as the plate boundary localized along nascent pull-apart basins in the northern Gulf of California, consistent with the hypothesis that late proto- Gulf of California dextral shear zones, such as the Coastal Sonora fault zone, acted to focus lithospheric-scale strain and promoted continental rupture in the wide-rift setting of the Mexican Basin and Range. [ABSTRACT FROM AUTHOR]

Abstract: Geologic mapping in the northern Sierra Los Ajos reveals new stratigraphic and structural data relevant to deciphering the Mesozoic–Cenozoic tectonic evolution of the range. The northern Sierra Los Ajos is cored by Proterozoic, Cambrian, Devonian, Mississippian, and Pennsylvanian strata, equivalent respectively to the Pinal Schist, Bolsa Quartzite and Abrigo Limestone, Martin Formation, Escabrosa Limestone, and Horquilla Limestone. The Proterozoic–Paleozoic sequence is mantled by Upper Cretaceous rocks partly equivalent to the Fort Crittenden and Salero Formations in Arizona, and the Cabullona Group in Sonora, Mexico. Absence of the Upper Jurassic–Lower Cretaceous Bisbee Group below the Upper Cretaceous rocks and above the Proterozoic–Paleozoic rocks indicates that the Sierra Los Ajos was part of the Cananea high, a topographic highland during the Late Jurassic and Early Cretaceous. Deposition of Upper Cretaceous rocks directly on Paleozoic and Proterozoic rocks indicates that the Sierra Los Ajos area had subsided as part of the Laramide Cabullona basin during Late Cretaceous time. Basal beds of the Upper Cretaceous sequence are clast-supported conglomerate composed locally of basement (Paleozoic) clasts. The conglomerate represents erosion of Paleozoic basement in the Sierra Los Ajos area coincident with development of the Cabullona basin. The present-day Sierra Los Ajos reaches elevations of greater than 2600m, and was uplifted during Tertiary basin-and-range extension. Upper Cretaceous rocks are exposed at higher elevations in the northern Sierra Los Ajos and represent an uplifted part of the inverted Cabullona basin. Tertiary uplift of the Sierra Los Ajos was largely accommodated by vertical movement along the north-to-northwest-striking Sierra Los Ajos fault zone flanking the west side of the range. This fault zone structurally controls the configuration of the headwaters of the San Pedro River basin, an important bi-national water resource in the US-Mexico border region. [Copyright &y& Elsevier]

Abstract: The El Barqueño district, Jalisco, consists of several polymetallic (Au–Ag–Cu–Zn–Pb) epithermal veins hosted by a volcanoplutonic assemblage of andesitic rocks, granites and granodiorites that belong to the Lower Volcanic Supergroup of the Sierra Madre Occidental. The paragenetic sequence indicates two main mineralization stages. Stage I occurs as breccias with base-metal sulfides and virtually no gold and silver. Stage II is made up of several crustiform quartz bands that form symmetrical vein fillings and contain the precious-metal mineralization. Rhombohedral adularia crystals and quartz pseudomorphs of bladed calcite are widespread in stage II, providing evidence for boiling. Au- and Ag-bearing metallic minerals locally precipitated directly on adularia crystals, an association indicating boiling as the main mechanism of metal deposition. Temperature and salinity of mineralizing fluids range from 101 to 252 °C and 0.2 to 19.1 wt.% NaCl equiv., respectively. While temperatures cluster in the range from 120 to 160 °C, salinities have a bimodal distribution, with most of them falling either below 3 wt.% NaCl equiv. or higher than 10 wt.% NaCl equiv. These two arrays of salinity values describe mixing trends only locally, and may reflect different sources of mineralizing fluids, possibly dominated by meteoric and magmatic sources, respectively. An adularia separate from stage II was dated by 40Ar/ 39Ar geochronology at 57.91±0.44 Ma (isochron age). Thus, El Barqueño is the oldest known epithermal deposit in Mexico, and suggests the existence of a previously unrecognized Paleocene metallogenic event in southwestern Mexico. [Copyright &y& Elsevier]

Abstract: Scattered ignimbritic mesas crop out in the Hermosillo region (Sonora, Mexico). These rocks that have been dated at 12.5 Ma (Middle Miocene) have the petrography and chemical characteristics of comendites. Such a flare-up of peralkaline acidic volcanism, after a long period of subduction-related arc volcanism, emphasises an important change in the source of volcanism. It corresponds to the latest stage of continental extension prior to the marine invasion and the development of spreading centres in the Gulf of California. To cite this article: J. Vidal Solano et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]

Early Cambrian volcanic rocks characterized by pyroclastic and lava flows of basaltic composition form the Cerro Rajón Formation are exposed in the Caborca region, northwest Sonora, Mexico. These rocks underwent greenschist facies metamorphism characterized by a metamorphic paragenesis of actinolite, sphene, chlorite, epidote and calcite with minor interstitial albite. This mineralogical association was characterized by electron microprobe analysis. Metamorphic temperatures were calculated by amphibole-plagioclase geothermometry, which indicates temperatures as high as 548 ± 40 °C. U Pb geochronology of the pluton that may cause the metamorphism yielded an age of 71.1 ± 0.4 Ma, and an average estimated temperature of 664 ± 40 °C. Preliminary pressures in this intrusive show an average of 3.08 ± 1.5 kbar. Two metamorphic events where identified by 40Ar/39Ar geochronology. Metabasalt samples from the western part of the study area yielded ages from 55.89 ± 0.6 Ma to 60.26 ± 0.33 Ma, while an age of 81.37 ± 0.81 Ma was obtained from a sample collected in the eastern part. Combined results suggest that Laramide intrusives metamorphosed the Neoproterozoic and Cambrian rocks in the Caborca region. • Caborca Cambrian volcanism is affected by Laramide metamorphism. • 40Ar/39Ar geochronology results show metamorphism ages of ∼60 Ma. • An U-Pb zircon age of 71.1 ± 0.4 Ma is reported for a nearby Laramide intrusive. • Cambrian metabasalts show greenschist facies metamorphism (T < 548 °C). • Caborca block successions were rapidly exhumed by basin and range. [ABSTRACT FROM AUTHOR]

Accurate information on the timing of earliest marine incursion into the Gulf of California (northwestern México) is critical for paleogeographic models and for understanding the spatial and temporal evolution of strain accommodation across the obliquely divergent Pacific-North America plate boundary. Marine strata exposed on southwest Isla Tiburón (SWIT) have been cited as evidence for a middle Miocene marine incursion into the Gulf of California at least 7 m.y. prior to plate boundary localization ca. 6 Ma. A middle Miocene interpretation for SWIT marine deposits has played a large role in subsequent interpretations of regional tectonics and rift evolution, the ages of marine basins containing similar fossil assemblages along ~1300 km of the plate boundary, and the timing of marine incursion into the Gulf of California. We report new detailed geologic mapping and geochronologic data from the SWIT basin, an elongate sedimentary basin associated with deformation along the dextral-oblique La Cruz fault. We integrate these results with previously published biostratigraphic and geochronologic data to bracket the age of marine deposits in the SWIT basin and show that they have a total maximum thickness of ~300 m. The 6.44 ± 0.05 Ma (Ar/Ar) tuff of Hast Pitzcal is an ash-flow tuff stratigraphically below the oldest marine strata, and the 6.01 ± 0.20 Ma (U/Pb) tuff of Oyster Amphitheater, also an ash-flow tuff, is interbedded with marine conglomerate near the base of the marine section. A dike-fed rhyodacite lava flow that caps all marine strata yields ages of 3.51 ± 0.05 Ma (Ar/Ar) and 4.13 ± 0.09 Ma (U/Pb) from the base of the flow, consistent with previously reported ages of 4.16 ± 1.81 Ma (K-Ar) from the flow top and (K-Ar) 3.7 ± 0.9 Ma from the feeder dike. Our new results confirm a latest Miocene to early Pliocene age for the SWIT marine basin, consistent with previously documented latest Miocene to early Pliocene (ca. 6.2-4.3 Ma) planktonic and benthic foraminifera from this section. Results from biostratigraphy and geochronology thus constrain earliest marine deposition on SWIT to ca. 6.2 ± 0.2 Ma, coincident with a regional-scale latest Miocene marine incursion into the northern proto-Gulf of California. This regional marine incursion flooded the northernmost, >500-km-long portion of the Gulf of California shear zone, a narrow belt of localized strike-slip faulting, clockwise block rotation, and subsiding pull-apart basins. Oblique Pacific-North America relative plate motion gradually localized in the >1000-km-long Gulf of California shear zone ca. 9-6 Ma, subsequently permitting the punctuated south to north flooding of the incipient Gulf of California seaway. [ABSTRACT FROM AUTHOR]

Paleozoic and Mesozoic stratigraphic sequences in the Puerto Libertad area, NW Sonora, Mexico, are intruded by Laramide granitic plutons with dominantly alkaline affinity. We conducted a petrogenetic study of these bodies across a north-south 35 km long transect at oriented NW-SE which includes the Sierra Picú (SP), El Destierro (ED), Sierra Tordilla (ST) and Sierra Los Mochos (SLM). The intrusive bodies display abundant Mafic Microgranular Enclaves (MME) and are intruded by aplitic and pegmatitic dike swarms. U/Pb zircon dates of the intrusive rocks yield crystallization ages between 71.9 and 74.9 Ma. Granodioritic and mozogranitic rocks dominate the SP and ED, while syenogranitic rocks dominate the ST and SLM regions. In addition, these rocks show notable effects, by normal and listric faults which includes cataclastic rocks. Geothermobarometry data from amphiboles and plagioclase of the granodiorites suggest that the temperatures and pressures reached 711–740 °C and 1.67–2.43 kb. respectively, and were emplaced at depths between ∼5 and 6 km. Geochemically, this magmatism shows a relatively high silica content (56–75 wt%), values of Sr/Y = 29–50, La/Yb = 26–39, Sr up to 600 ppm and Ba up to 1400 ppm and depleted in highfield strength elements. Collectively these geochemical traits accentuate the adakite signature of these rocks. This work raises the current problems related to the petrogenetic and tectonic aspects for the generation of calc-alkaline and adakitic magmas while proposing ternary discrimination diagrams to aid in the discrimination from classic calk-alkaline, adakites and adakitic affinity magmatism. • Geochronology analyses from intrusives yield crystallization ages between 71.9 and 74.9 Ma. • Geothermobarometry show temperatures and pressures reached 711–740 °C and 1.67–2.43 kb. • Northern localities show adakitic signatures while Sierra Los Mochos show adakitic affinity. • We propose discrimination diagrams between calc-alkaline, adakites and adakitic affinity magmas. [ABSTRACT FROM AUTHOR]

The El Álamo is one of the most important historic gold mining districts in the Peninsular Ranges batholith. Gold mineralizations at El Álamo consist in fault-fill laminated quartz veins with small amounts of sulfides and oxides, and lesser amounts of gold. Veins are mainly emplaced along compressional brittle-plastic shear zones within the El Álamo quartz diorite (146.6 ± 1.6 Ma, U–Pb zircon), which is intruded by the San Marcos dike swarm (126.8 ± 1.7 Ma, U–Pb zircon). Several lines of evidence indicate that the dike swarm is older than quartz veins, and the formation of the later is related to the Peninsular Ranges orogeny (∼110−98 Ma). Gold bearing quartz veins formed during regional prograde metamorphism (greenschist facies), and the veins subsequently underwent plastic deformation, dynamic recrystallization and metamorphism. Gold remobilization and concentration seems to have been largely enhanced by metamorphism, probably accounting for very high grade, albeit sporadic, bonanza ores, typical of the district. 40Ar/39Ar dating of hydrothermal white micas from the auriferous veins yielded ages of 97.86 ± 0.17 Ma at the Ulises mine and 97.46 ± 0.17 Ma at the La Americana mine. These ages are interpreted as the minimum age of the regional metamorphism in the area. Based on their primary characteristics, the gold deposits from El Álamo district can be ascribed to the orogenic gold type. These deposits are similar to other known deposits in the same orogenic context (e.g., Julian district; southern California), and they probably conform a new Cordilleran orogenic gold belt that could extend over much of the exhumed axis of the Peninsular Ranges batholith. [Display omitted] • The El Álamo deposits are formally described as part of the orogenic gold type. • These deposits may constitute a part of a new Cordilleran orogenic gold belt. • Gold-bearing quartz veins formed during prograde phase of the mid-Cretaceous metamorphic event in the Peninsular Ranges batholith. • Gold deposits underwent plastic deformation, dynamic recrystallization and metamorphism (upper-greenschist facies) affecting gold concentration. [ABSTRACT FROM AUTHOR]

Stratigraphy, sedimentology, and geochronology of the Upper Jurassic Cucurpe Formation in north-central Sonora, Mexico, provide new insights into Late Jurassic rifting along the southwestern margin of Laurentia. The Cucurpe Formation is the fill of the Altar-Cucurpe Basin. This basin developed upon attenuated crust of the Triassic-Middle Jurassic continental arc and was part of the Arivechi-Cucurpe seaway; a narrow marine embayment oriented parallel to and located west of the Chihuahua trough. The Cucurpe Formation unconformably overlies Middle Jurassic arc assemblages and represents upward-coarsening marine prodeltaic deposits. New U-Pb zircon geochronology and a Kimmeridgian ammonite (Idoceras cf. I. densicostatum) constrain its age to between ca. 158 and 149 Ma. Detrital zircon ages from the unconformably overlying Lower Cretaceous Bisbee Group indicate a maximum depositional age of 139 ± 2 Ma (2 error), demonstrating a hiatus of at least 10 m.y. between Jurassic and Cretaceous strata. Detrital zircon ages and petrographic data indicate the provenance of Cucurpe Formation and lowermost Bisbee strata. The lower part of the Cucurpe was derived dominantly from Middle Jurassic volcano-sedimentary successions. Theupper part of the Cucurpe Formation was largely derived from syneruptive volcanic material equivalent to the Ko Vaya volcanic suite of southern Arizona and northern Sonora. Lowermost Bisbee strata were derived from Middle Jurassic arc rocks and exhumed Caborcan basement, Paleozoic-Lower Jurassic sedimentary cover, and Lower Cretaceous intermediate volcanic rocks. Revised stratigraphy of the Cucurpe- Tuape region indicates that several conglomeratic units, formerly interpreted as Late Jurassic pull-apart basin deposits, are not of Late Jurassic age. [ABSTRACT FROM AUTHOR]

Stratigraphic relationships, detrital zircon provenance, U-Pb and 40Ar/39Ar geochronology, and trace element geochemistry in volcanic and sedimentary rocks of the Sierra homocline of central Chiapas near La Angostura reservoir in Mexico document an extensive pulse of Early-Middle Jurassic arc magmatism in rocks that overlie and intrude the Permian-Triassic Chiapas massif. Upper Jurassic rift-basin strata unconformably overlie the volcanic rocks and the massif. A Pliensbachian U-Pb (zircon) SHRIMP (sensitive high-resolution ion microprobe) age from porphyritic andesite (191.0 ± 3.0 Ma), Early to Middle Jurassic 40Ar/39Ar dates from andesitic dikes, U-Pb grain ages of detrital zircons in overlying strata (196- 161 Ma), and previously reported K-Ar dates indicate that subduction-related magmatism occurred in the western portion of the Maya block from Early to latest Middle Jurassic time. We assign the volcanic rocks to the La Silla Formation, which correlates with the informal Pueblo Viejo andesite of the Cintalapa and Uzpanapa regions to the northwest. La Silla magmatism predates opening of the Gulf of Mexico Basin. The Todos Santos Formation, which overlies La Silla Formation, was deposited in extensional basins during the early stages of gulf opening. We recognize a lower El Diamante Member of the Todos Santos, consisting of red fl uvial sandstone, mudstone, and minor conglomerate containing primarily volcanic-lithic detritus; this member is characterized by a nearly unimodal Jurassic detrital zircon age population that indicates a Callovian or younger depositional age. Volcanic activity continued into the upper part of the El Diamante Member, but with a more mafi c character. We also recognize an upper member, which we term the Jericó Member. This member is characterized by thickly bedded, coarse-grained pebbly arkose intercalated with several thick intervals (tens of meters) of conglomerate and pebbly sandstone. Sandstone petrology indicates a source in the granitic rocks of the Chiapas massif, with a tendency to show deep-seated sources and a diverse zircon population in the upper part of the section. The upper Todos Santos Formation in the study area is gradational into the overlying San Ricardo Formation ( Kimmeridgian- Tithonian ). The La Silla Formation was deposited in volcanic-complex environments, with a clear lack of differentiated vol canic rocks. Fluvial strata of the El Diamante Member were deposited in a mud-rich sinuous river system. The Jericó Member was deposited in large, sand-rich fluvial systems, which probably represent deposits of riftaxis trunk streams; conglomerate facies were deposited in adjacent and interfingering alluvial fan systems. We suggest that the stratigraphic record of the western Maya block records a transition from volcanic arc to intra-arc basin and subsequently to rift basin during Pliensbachian to Oxfordian time. [ABSTRACT FROM AUTHOR]

A remarkable suite of Miocene high-silica trondhjemites discovered in the central Trans-Mexican Volcanic Belt indicates that slab melts can ascend through the mantle and crust while suffering only minor compositional modifications. Despite carrying an assortment of deep crustal xenoliths, the trondhjemites preserve the most depleted isotopic compositions ever measured in the Mexican arc, with values that are nearly identical to those of the Pacific mid-oceanic-ridge basalts. These rocks also have high Sr/Y ratios, and extremely fractionated heavy rare earth element patterns at relatively high Mg number (Mg#), features that are all consistent with melts from the subducted oceanic crust that had only limited interaction with mantle peridotite during ascent. Nonetheless, modeling results indicate that these unusual geochemical features can be modified by more extensive mantle assimilation, resulting in compositions that could match those of more typical intermediate rocks from Mexico. The data thus indicate that the slab melt component uniquely recorded by the Miocene trondhjemites represents a likely constituent for most volcanic sequences of the Mexican arc, and suggest that a modern andesitic continental crust can be constructed directly from mantle-modified slab melts without a basaltic precursor. [ABSTRACT FROM AUTHOR]

This is a Reply to Calmus and collaborators' comment about our publication entitled: "Geochronology and geothermometry of the Laramide metamorphism in the Cambrian metabasalts from the Cerro Rajón Formation, Caborca region, northwest Mexico". The authors reevaluate our geothermobarometry data using a different calibration reaction which yields lower metamorphic temperatures for the metabasalts in the Cerro Rajón Formation. They also reinterpret the metamorphism as regional metamorphism based on the deformation caused by the Laramide orogeny in northwestern Sonora. We consider the lower metamorphism temperatures as a suitable alternative or a lower limit for a metamorphic temperature range, although they have no effect on our interpretations. Nevertheless, we disagree with the hypothesis of an orogenic metamorphism as a viable alternative, considering that the Cerro Rajón Formation lacks any kind of schistosity and it shows, at the most, a low degree of deformation. Finally, we present re-calculations from the Cerro El Dátil laramidic intrusive to adjust the previously obtained interpretations. • Geothermometry results show a range of metamorphic temperatures from 400 to 500 °C. • The Cerro Rajón Formation show evidence of a contact metamorphism. • Regional metamorphism should not be considered due to the lack of schistosity. • Recalculated geobarometry pressures indicate a depth of emplacement of 4 km. [ABSTRACT FROM AUTHOR]