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James V. Jones

Publications and source records attributed to James V. Jones.

At least 19 recordsLinked to original sources
USGS2026

USGS 2025 critical minerals review

The United States Geological Survey (USGS) provides scientific information for the Department of Interior and the nation, consistent with its original mission expressed in the Organic Act of 1879 (43 U.S.C. 31): “the classification of the public lands and examination of the geological structure, mineral resources, and products within and outside the national domain.” Legislation such as the Energy Act of 2020 and the 2022 Infrastructure Investment and Jobs Act (43 USC 31l) and recent executive actions (Executive Orders 14154 , 14153, 14241 Secretary’s Orders 3417, 3418, 3422, 3436) underscore the importance of mineral resources and focus USGS activities on mapping and assessing mineral resources, with a particular focus on those presently identified as critical, both in ground and above ground in mine wastes. This article reviews selected activities and accomplishments by the USGS Mineral Resources Program related to critical minerals in 2025. Highlights include a new List of Critical Minerals, a first-ever national mine waste inventory, international minerals partnerships, mineral resource assessment advancements, and national data collection activities and outcomes of the Earth Mapping Resources Initiative (Earth MRI). The selected contributions are not comprehensive but are intended to demonstrate USGS leadership in critical mineral mapping and assessment, the importance of domestic and global partnerships, and the breadth of research activities that are responsive to national needs and priorities.

Mining Engineering↗
USGS2026

Integrating detrital magnetite geochemistry and (U-Th)/He chronometry as a sediment provenance tool in geologic and metallogenic terranes

Magnetite is ubiquitous in porphyry Cu systems and in sediment sourcing both barren and mineralized regions, with potential as an indicator mineral in concealed and coarsely-mapped terranes. We develop and test a workflow for integrated geochemistry and (U–Th)/He (He) dating for inferring detrital magnetite (DMt) provenance in these settings. The ca. 70 Ma Taurus porphyry Cu–Mo(–Au) district in eastern interior Alaska serves as a test case. DMt from streams draining porphyry-related mineralization was characterized by geochemistry and mineral inclusion and microstructure observations, complemented by similar data for potential porphyry and host rock sources. Principal component analysis and clustering of DMt geochemical data resolve multiple populations in our samples geochemically and texturally compatible with derivation from metamorphic, porphyry-related hydrothermal, and igneous sources. Hydrothermal magnetite comprises ∼16–50% of DMt nearest porphyry mineralization but diminishes to ∼4% ∼15 km downstream. Subsampled grains within populations yield ∼160–110 Ma, ∼70 Ma, ∼55 Ma, and ∼20 Ma magnetite He date modes. Combined with provenance, He dates capture Early Cretaceous regional exhumation of metamorphic host rock and Late Cretaceous porphyry Cu mineralization. DMt grains showing partial hematite replacement yield ca. 55–20 Ma dates regardless of source, overlapping regional warm/wet climatic intervals. We interpret Cenozoic dates to reflect exhumation to near-surface oxidizing conditions and(or) supergene weathering. Magnetite is thus a promising target phase for (1) tracking the spatiotemporal distribution of porphyry systems, and (2) linking the formation and exhumation of these systems to a regional geologic history, both in Alaska and globally.

Alaska, Yukon↗
USGS2025

Evidence for offset of Cretaceous plutons by the Tintina fault in eastern Alaska: Implications for regional metallogeny

Cretaceous magmatism in eastern interior Alaska is voluminous, but temporally and spatially diverse – suggestive of varying sources and drivers. More than 150 new U-Pb zircon and more than 500 geochemical analyses of Cretaceous plutonic units allow for the grouping of distinct plutonic suites. Magmatism was continuous from 120-66 Ma but can be grouped into temporally distinct pulses from ca. 115-100 Ma, 100-90 Ma, and 75-66 Ma. Geochemical diversity occurs during each pulse, further distinguishing multiple suites. Diverse metallogenic epochs are strongly correlated to pluton chemistry. Mineralization is largely absent prior to 108 Ma. From 108-100 Ma, plutonism is coeval with sparse, but notable Au-quartz veins with variable Bi, As, W, and Mo. From 100-90 Ma, intrusion-related mineralization zones from Au-Cu(-Bi) and U-Th in the northwest to central Au- Bi-As-Te(-W), and Mo-W to the southeast. Porphyry style Cu-Mo(-Au) occurrences occur with the latest Cretaceous plutons emplaced from 75-66 Ma . Restoration of ~450 km of dextral movement on the Tintina fault and comparison of metallogenic and geochemical characteristics of Alaska plutons suggest 100-90 Ma plutons may be the continuation of the metallogenically significant Tombstone, Mayo, and Tungsten suites from the Yukon.

Alaska↗
USGS2023

Rapid active thrust faulting at the northern Alaska Range front

Plate convergence rates strongly influence seismicity and mountain building inboard of convergent margins, but the distribution and kinematics of structures accommodating farfield convergence can be elusive. In interior Alaska, Yakutat microplate convergence drives late Pleistocene–recent right slip on the Denali fault, but westward-decreasing slip rates leave substantial residual Yakutat motion unaccounted for. Here, we show that Northern Foothills thrust slip beneath the northern Alaska Range absorbs a modern 4.4 mm/yr geodetic velocity gradient equivalent to ~78% of the 5.6 mm/yr residual Yakutat convergence along the central Denali fault. Infrared-stimulated luminescence ages of strath terrace deposits (67–4 ka; six sites) quantify Totatlanika River bedrock incision across the 1947 M w 7.1 thrust earthquake epicentral region. Incision rates increase abruptly from <1 mm/yr to 4.8–5.6 mm/yr above the blind thrust tip near the range front. Rapid slip at 6.7 mm/yr on a steep thrust ramp beneath the northern Alaska Range front accommodates the geodetic gradient, drives rock uplift at rates matching measured incision rates, and implies that large earthquakes like the 1947 event may recur with 500–1400 yr frequency. Results illuminate focused seismogenic strain inboard of a complex convergent margin and prompt reevaluation of Alaska’s neotectonic framework.

Alaska↗
USGS2022

Alaska focus area definition for data acquisition for potential domestic sources of critical minerals in Alaska for antimony, barite, beryllium, chromium, fluorspar, hafnium, magnesium, manganese, uranium, vanadium, and zirconium

Phase 3 of the Earth Mapping Resources Initiative (Earth MRI) focuses on geologic belts that are favorable for hosting mineral systems that could contain the critical minerals antimony, barite, beryllium, chromium, fluorspar, hafnium, magnesium, manganese, uranium, vanadium, and zirconium. Prior phases of the Earth MRI program in Alaska focused only on rare earth elements, aluminum, cobalt, graphite, lithium, niobium, platinum-group metals, tantalum, tin, titanium, and tungsten. An additional 11 critical minerals planed for future phases of Earth MRI (As, Bi, Cs, Ga, Ge, In, Re, Rb, Sc, Sr, Te) are considered prospective in these focus areas. Together, Alaska focus areas address 22 of the 35 minerals or mineral material groups presently deemed critical. This report describes the methodology and techniques utilized to define focus areas for future data acquisition in Alaska; the conterminous United States are covered in a separate report. Focus areas are identified using a mineral systems framework, which accounts for all the possible tectonic and geologic settings where co-genetic mineral deposits may form. These deposits contain many commodities, including byproduct and critical minerals. Large system-scale processes may be evaluated using such a framework to determine the influence they play on critical mineral endowment within the deposits. Analyzing larger mineral systems provides an integrated and broad context to determine how and where critical minerals are sourced, transported, and deposited in geologic systems. Statewide geological, geochemical, geophysical, and mineral occurrence datasets informed the delineation of focus areas in Alaska. For some mineral systems, previously published data-driven prospectivity analyses for critical mineral-bearing deposit types provided the basis for focus areas. We report a total of 22 new focus areas that are prospective for phase 3 critical minerals. These new focus areas represent four different mineral systems that are known or suspected to occur in Alaska. An additional 55 focus areas that were previously identified for phase 1 and phase 2 commodities were also identified as being prospective for phase 3 critical minerals. Collectively, 102 focus areas in Alaska have known or suspected potential for hosting phase 1, phase 2, and (or) phase 3 critical minerals. These focus areas represent 17 different mineral systems also containing critical minerals that are planned for consideration in future Earth MRI phases. Thus, the focus areas delineated herein, and in previous reports for Alaska, are comprehensive for all critical minerals as presently defined and may be used to guide the collection of new geologic, geochemical, and geophysical data in the region.

Alaska↗
USGS2022

Laurentia in transition during the Mesoproterozoic: Observations and speculation on the ca. 1500–1340 Ma tectonic evolution of the southern Laurentian margin

An accretionary tectonic model for the Mesoproterozoic ca. 1500–1340 Ma tectonic evolution of the southern Laurentian margin is presented. The tectonic model incorporates key observations about the nature and timing of Mesoproterozoic deposition, magmatism, regional metamorphism, and deformation across the 5000-km-long southern Laurentian margin. This time period was one of transition in the supercontinent cycle and occurred between the breakup of Columbia and the formation of Rodinia, and the southern Laurentian margin was a significant component of a much greater accretionary margin extending into Baltica and Amazonia and possibly parts of Antarctica and Australia. However, fundamental questions and contradictions remain in our understanding of the tectonic evolution of Laurentia and paleogeography during this time interval.

Book chapter↗
USGS2022

Circa 1.50–1.45 Ga metasedimentary rocks in southwestern Laurentia provide distinctive records of Mesoproterozoic regional orogenesis and craton interactions

The discovery of multiple deformed and metamorphosed sedimentary successions in southwestern Laurentia that have depositional ages between ca. 1.50 and 1.45 Ga marked a turning point in our understanding of the Mesoproterozoic tectonic evolution of the continent and its interactions with formerly adjacent cratons. Detrital zircon U-Pb ages from metasedimentary strata and igneous U-Pb zircon ages from interbedded metavolcanic rocks in Arizona and New Mexico provide unequivocal evidence for ca. 1.50–1.45 Ga deposition and burial, followed by ca. 1.45 and younger deformation, metamorphism, and plutonism. These events reflect regional shortening and crustal thickening that are most consistent with convergent to collisional orogenesis—the Mesoproterozoic Picuris orogeny—in southwestern Laurentia. Similar metasedimentary successions documented in the midcontinent of the United States and in eastern Canada help to establish ca. 1.45 Ga orogenesis as a continent-scale phenomenon associated with a complex and evolving convergent margin along southern Laurentia. Metasedimentary successions of similar age are also exposed across ~5000 km of the western Laurentian margin and contain distinctive 1.6–1.5 Ga detrital zircon populations that are globally rare except in select cratonic provinces in Australia and Antarctica. The recognition of these distinctive detrital zircon ages provides a transient record of plate interactions prior to breakup of Nuna or Columbia ca. 1.45 Ga and provides key constraints on global plate reconstructions.

GSA Memoirs↗
USGS2022

Late Paleoproterozoic to early Mesoproterozoic deposition of quartz arenites across southern Laurentia

Supermature siliciclastic sequences were deposited between 1.64 Ga and 1.59 Ga over a broad swath of southern Laurentia in the Archean, Penokean, Yavapai, and Mazatzal Provinces. These siliciclastic sequences are notable for their extreme mineralogical and chemical maturity, being devoid of detrital feldspar and ferromagnesian minerals, containing the clay mineral kaolinite (or its metamorphic equivalent, pyrophyllite), and having a chemical index of alteration >95. Such maturity is the result of a perfect confluence of tectonic and climatic conditions, including a stable continental crust with low topographic relief (the Archean, Penokean, and Yavapai Provinces ca. 1.70 Ga), a warm humid climate, an elevated level of atmospheric CO 2 , and relatively acidic pore fluids in the critical zone. The weathered detritus was transported and deposited by southward-flowing streams across the Archean, Penokean, and Yavapai Provinces, ultimately to be deposited on 1.66 Ga volcanic and volcaniclastic rocks in the Mazatzal continental arc along the southern margin of Laurentia.

Laurentia↗
USGS2022

Yukon River incision drove organic carbon burial in the Bering Sea during global climate changes at 2.6 and 1 Ma

River erosion affects the carbon cycle and thus climate by exporting terrigenous carbon to seafloor sediment and by nourishing CO 2 -consuming marine life. The Yukon River–Bering Sea system preserves rare source-to-sink records of these processes across profound changes in global climate during the past 5 million years (Ma). Here, we expand the terrestrial erosion record by dating terraces along the Charley River, Alaska, and explore linkages among previously published Yukon River tributary incision chronologies and Bering Sea sedimentation. Cosmogenic 26 Al / 10 Be "> isochron burial ages of Charley River terraces match previously documented central Yukon River tributary incision from 2.6 to 1.6 Ma during Pliocene–Pleistocene glacial expansion, and at 1.1 Ma during the 1.2–0.7 Ma Middle Pleistocene climate transition. Bering Sea sediments preserve 2–4-fold rate increases of Yukon River-derived continental detritus, terrestrial and marine organic carbon, and silicate microfossil deposition at 2.6–2.1 and 1.1–0.8 Ma. These tightly coupled records demonstrate elevated terrigenous nutrient and carbon export and concomitant Bering Sea productivity in response to climate-forced Yukon River incision. Carbon burial related to accelerated terrestrial erosion may contribute to CO 2 drawdown across the Pliocene–Pleistocene and Middle Pleistocene climate transitions observed in many proxy records worldwide.

Alaska, British Columbia, Northwest Territories, Y↗
USGS2021

Tectonic and magmatic controls on the metallogenesis of porphyry deposits in Alaska

Porphyry Cu and Mo deposits and occurrences are found throughout Alaska; they formed episodically during repeated subduction and arc-continent collisions spanning the Silurian to Quaternary. Porphyry systems occur in continental-margin and island arcs, which are broadly grouped into pre-accretionary or post-accretionary arcs. Pre-Mesozoic occurrences formed in continental or island arcs prior to accretion onto the margin of North America, whereas Mesozoic and younger systems formed in arcs that developed after terrane fragments were accreted to the margin of North America. As a result, older porphyry systems are typically in the interior and northern metallogenic belts, whereas the younger porphyry systems are predominantly found in the southern third of the state, closer to the modern continental margin. Alaska porphyry formation peaked in the mid-Cretaceous and continued through the Late Cretaceous to Tertiary, in association with continental-margin arcs extending from the eastern interior, into southwest Alaska and along the Alaska Peninsula and Aleutian Islands. Porphyry system formation is not generally recognized in the Early Cretaceous, Triassic, or early Paleozoic – time periods that coincide with continental collisional events or extension. Relatively few pre-accretionary porphyry systems are documented in more deeply exhumed arc segments due to low preservation potential in areas of rapid or repeated bedrock uplift and associated erosion that occurred during later tectonic events. Significant diversity is observed in porphyry occurrences across the state and even within the same region. Occurrences form in association with arc-related intrusions or intrusive complexes, that range in composition from diorite to syenite, but are commonly monzonitic to granitic. Some porphyry occurrences are associated with alkaline intrusive belts that exhibit a stronger crustal contribution to magmatic sources. Intrusions associated with porphyry formation in Alaska are commonly moderately oxidized, however, a distinct group of porphyry systems are associated with more-reduced magmas. Hydrothermal alteration described at many occurrences exhibits zoning from proximal potassic alteration to typically peripheral and(or) later sericitic alteration, that is flanked by large zones of propylitic alteration. Diversity in alteration is observed where sodic and sodic-calcic alteration is present, commonly in more-enigmatic deposits, such as Island Mountain and Chicken Mountain. Advanced argillic alteration is rare, but present in notable examples, such as the Pebble porphyry Cu(-Au-Mo) deposit. Sulfide mineralization is characterized by pyrite, chalcopyrite, molybdenite, and rare bornite hosted in veinlets, veins and disseminations in wallrocks and causative intrusions. Some porphyry systems contain abundant pyrrhotite and(or) arsenopyrite in the mineral assemblages. Systems that exhibit bornite-bearing assemblages containing abundant molybdenite are commonly arsenic- and gold-poor and tend to be associated with more oxidized arc magmas. In contrast, those systems that are pyrrhotite and(or) arsenopyrite dominant tend to be gold, arsenic, and bismuth bearing, and are commonly associated with more-reduced magmas. Exploration for porphyry occurrences in Alaska has experienced a resurgence and currently constitutes about 20% of exploration dollars in the state. Many systems lack complete descriptions, and coupled with the cost of exploration, remain incompletely explored. Additional understanding of known occurrences combined with a framework geologic understanding of porphyry-bearing metallogenic belts will likely result in new discoveries in the future.

Alaska↗
USGS2020

Cretaceous to Oligocene magmatic and tectonic evolution of the western Alaska Range: Insights from U-Pb and 40Ar/39Ar geochronology

New U-Pb and 40 Ar/ 39 Ar ages integrated with geologic mapping and observations across the western Alaska Range constrain the distribution and tectonic setting of Cretaceous to Oligocene magmatism along an evolving accretionary plate margin in south-central Alaska. These rocks were emplaced across basement domains that include Neoproterozoic to Jurassic carbonate and siliciclastic strata of the Farewell terrane, Triassic and Jurassic plutonic and volcanic rocks of the Peninsular terrane, and Jurassic and Cretaceous siliciclastic strata of the Kahiltna assemblage. Plutonic rocks of different ages also host economic mineralization including intrusion-related Au, porphyry Cu-Mo-Au, polymetallic veins and skarns, and peralkaline intrusion-related rare-earth elements. The oldest intrusive suites were emplaced ca. 104–80 Ma into the Peninsular terrane only prior to final accretion. Deformation of the northern Kahiltna succession and underlying Farewell terrane occurred at ca. 97 Ma, and more widespread deformation ca. 80 Ma involved south-vergent folding and thrusting of the Kahiltna assemblage that records collisional accretion of the Peninsular-Wrangellia terrane and juxtaposition of sediment wedges formed on the inboard and outboard terranes. More widespread magmatism ca. 75–55 Ma occurred in two general pulses, each having distinct styles of localized deformation. Circa 75–65 Ma plutons were emplaced in a transpressional setting and stitch the accreted Peninsular and Wrangellia terranes to the Farewell terrane. Circa 65–55 Ma magmatism occurred across the entire range and extends for more than 200 km inboard from the inferred position of the continental margin. The Paleocene plutonic suite generally reflects shallower emplacement depths relative to older suites and is associated with more abundant andesitic to rhyolitic volcanic rocks. Deformation ca. 58–56 Ma was concentrated along two high-strain zones, the most prominent of which is 1 km wide, strikes east-northeast, and accommodated dextral oblique motion. Emplacement of widespread intermediate to mafic dikes ca. 59–51 Ma occurred before a notable magmatic lull from ca. 51–44 Ma reflecting a late Paleocene to early Eocene slab window. Magmatism resumed ca. 44 Ma, recording the transition from slab window to renewed subduction that formed the Aleutian-Meshik arc to the southwest. In the western Alaska Range, Eocene magmatism included emplacement of the elongate north-south Merrill Pass pluton and large volumes of ca. 44–37 Ma andesitic flows, tuffs, and lahar deposits. Finally, a latest Eocene to Oligocene magmatic pulse involved emplacement of a compositionally variable but spatially concentrated suite of magmas ranging from gabbro to peralkaline granite ca. 35–26 Ma, followed by waning magmatism that coincided with initiation of Yakutat shallow-slab subduction. Cretaceous to Oligocene magmatism throughout the western Alaska Range collectively records terrane accretion, translation, and integration together with evolving subduction dynamics that have shaped the southern Alaska margin since the middle Mesozoic.

Alaska↗
USGS2020

Focus areas for data acquisition for potential domestic resources of 11 critical minerals in Alaska—Aluminum, cobalt, graphite, lithium, niobium, platinum group elements, rare earth elements, tantalum, tin, titanium, and tungsten, chap. C of U.S. Geological Survey, Focus areas for data acquisition for potential domestic sources of critical minerals

Phase 2 of the Earth Mapping Resources Initiative (Earth MRI) focuses on geologic belts that are favorable for hosting mineral systems that may contain select critical minerals. Phase 1 of the Earth MRI program focused on rare earth elements (REE), and phase 2 adds aluminum, cobalt, graphite, lithium, niobium, platinum-group metals, tantalum, tin, titanium, and tungsten. This report describes the methodology and techniques utilized to define focus areas for future data acquisition in Alaska; the conterminous United States are covered in a separate report. Definition of focus areas relies on a mineral systems framework that considers geologic features that may influence or control the formation and preservation of a mineral deposit and links the critical commodities to genetically related processes. Mineral systems are therefore larger than any given deposit. Evaluation of these larger systems allows for a broader understanding of how and where critical minerals may move through geologic systems. Delineation of focus areas in Alaska was informed by statewide geological, geochemical, geophysical, and mineral occurrence datasets that are publicly available. Additionally, previously published prospectivity analyses for six different critical mineral-bearing deposit types help identify focus areas. A total of 74 focus areas prospective for the phase 2 critical minerals that occur in 12 different mineral systems were defined in Alaska. Identified focus areas may be used to guide future geologic, geochemical, and geophysical data in the State of Alaska.

Alaska↗
USGS2020

Imaging the tectonic grain of the Northern Cordillera orogen using Transportable Array receiver functions

Azimuthal variations in receiver function conversions can image lithospheric structural contrasts and anisotropic fabrics that together compose tectonic grain. We apply this method to data from EarthScope Transportable Array in Alaska and additional stations across the northern Cordillera. The best‐resolved quantities are the strike and depth of dipping fabric contrasts or interfaces. We find a strong geographic gradient in such anomalies, with large amplitudes extending inboard from the present‐day subduction margin, the Aleutian arc, and an influence of flat‐slab subduction of the Yakutat microplate north of the Denali fault. An east–west band across interior Alaska shows low‐amplitude crustal anomalies. Anomaly amplitudes correlate with structural intensity (density of aligned geological elements), but are the highest in areas of strong Cenozoic deformation, raising the question of an influence of current stress state. Imaged subsurface strikes show alignment with surface structures. We see concentric strikes around arc volcanoes implying dipping magmatic structures and fabric into the middle crust. Regions with present‐day weaker deformation show lower anomaly amplitudes but structurally aligned strikes, suggesting pre‐Cenozoic fabrics may have been overprinted or otherwise modified. We observe general coherence of the signal across the brittle‐plastic transition. Imaged crustal fabrics are aligned with major faults and shear zones, whereas intrafault blocks show imaged strikes both parallel to and at high angles to major block‐bounding faults. High‐angle strikes are subparallel to neotectonic deformation, seismicity, fault lineaments, and prominent metallogenic belts, possibly due to overprinting and/or co‐evolution with fault‐parallel fabrics. We suggest that the underlying tectonic grain in the northern Cordillera is broadly distributed rather than strongly localized. Receiver functions thus reveal key information about the nature and continuity of tectonic fabrics at depth and can provide unique insights into the deformation history and distribution of regional strain in complex orogenic belts.

Alaska↗
USGS2020

Geochronologic and Hf-isotope framework of Proterozoic rocks from central New Mexico, USA: Formation of the Mazatzal crustal province in an extended continental margin arc

The growth of southern Laurentia has been attributed to the accretion of juvenile arc terranes during the successive 1.74-1.68 Ga Yavapai and 1.65-1.60 Ga Mazatzal orogenies. However, in light of the increasing importance of the ca. 1.49-1.40 Ga Mesoproterozoic Picuris orogeny, the tectonic setting in which the Mazatzal crustal province and its distinctive quartzite-rhyolite successions were generated needs additional examination. The Sandia-Manzano-Los Pinos uplift in central New Mexico is an ideal place to characterize the tectonic history of the Mazatzal crustal province. A comprehensive geochronologic and Hf-isotopic dataset for Proterozoic rocks of the Sandia-Manzano-Los Pinos uplift is presented. Plutonic and metavolcanic rocks in the Sandia-Manzano-Los Pinos uplift were emplaced in three pulses at 1668-1655 Ma, 1587 Ma, and 1459-1453 Ma. Hf-isotope data from the Paleoproterozoic plutonic rocks are juvenile, with both leucogranite and arc-related granodiorite yielding εHf(t) values ranging from +6 to +12, compared to the coeval depleted mantle value of +10 at ca. 1.65 Ga. Inherited zircon in Paleoproterozoic rocks suggest that crust older than 1.7 Ga was involved in their genesis. Hf-isotope data from Mesoproterozoic plutonic rocks in the Sandia-Manzano-Los Pinos uplift are consistent with derivation from 1.7-1.6 Ga lithosphere. Detrital zircon indicate that metasedimentary rocks of the lower Manzano Group were derived primarily from local sources that have U-Pb-Hf isotope compositions similar to the plutonic rocks which intrude and volcanic rocks that underlie the Manzano Group. The detrital zircon provenance of the Manzano Group broadens up-section from unimodal populations with age peaks at ca. 1.65 Ga to include 1.7-3.0 Ga detrital zircon derived from older Laurentian sources like the Yavapai and Mojave provinces. We offer a new model for the formation of the Mazatzal crustal province of New Mexico as a continental margin arc built on top of the previously assembled Yavapai province. The Manzano Group quartzite-rhyolite succession was formed by lithospheric extension above a north-dipping, southward retreating subduction zone. The Manzano Group was then subjected to ca. 1.65 Ga syn-magmatic tectonism and later intracratonic contractional tectonism, likely during the 1.46-1.40 Ga Picuris orogeny.

New Mexico↗
USGS2020

U-Pb Zircon ages from bedrock samples collected in the Tanacross D-1, and parts of the D-2, C-1, and C-2 quadrangles, Alaska

This Alaska Division of Geological & Geophysical Surveys (DGGS) Preliminary Interpretive Report presents U-Pb ages of zircons from 14 sedimentary, metamorphic, and igneous samples collected during 2017 and 2018 field investigations in the northeastern Tanacross Quadrangle, Alaska. The DGGS Northeast Tanacross project is a part of multi-year effort to investigate the geology and mineral-resource potential of the Yukon-Tanana Uplands region in collaboration with the U.S. Geological Survey. The purpose of the U-Pb isotopic study is to better understand the Devonian-to-Mississippian and Mesozoic-to-Early Paleogene episodes of magmatic and tectonic events within the Yukon-Tanana Uplands and the relationship of magmatism to the metallic mineral deposits. This area is characterized by the presence of two Late Devonian to Mississippian metamorphic assemblages-Lake George and Fortymile River (Dusel-Bacon and others, 2006; Foster, 1970). Both assemblages are composed of metasedimentary and metavolcanic rocks that have been intruded by Devonian to Eocene intrusive rocks of varying composition and texture. Paleozoic intrusive rocks are deformed and metamorphosed and include prevalent Late Devonian-Early Mississippian augen orthogneiss, herein called the Divide Mountain suite, that was emplaced into and deformed together with the Lake George assemblage (Aleinikoff and others, 1986). The Fortymile River assemblage is primarily cross-cut by Mississippian to Permian intrusive rocks that are also pervasively deformed and metamorphosed. Following Jurassic to mid-Cretaceous regional metamorphism and deformation, all metamorphic rock packages were intruded by Mid- to Late-Cretaceous volcanic and plutonic rocks (Naibert and others, 2018), some of which have known or suspected potential for gold together with silver, zinc, copper, and lead mineralization. Products included in this data release are: A summary of sample-collection methods, the laboratory report, analytical data tables, and associated metadata. All components of this data release are available on the DGGS website http://doi.org/10.14509/30465 .

Alaska↗