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Murray W. Hitzman

Publications and source records attributed to Murray W. Hitzman.

8 recordsLinked to original sources
USGS2017

Cobalt—Styles of deposits and the search for primary deposits

Cobalt (Co) is a potentially critical mineral. The vast majority of cobalt is a byproduct of copper and (or) nickel production. Cobalt is increasingly used in magnets and rechargeable batteries. More than 50 percent of primary cobalt production is from the Central African Copperbelt. The Central African Copperbelt is the only sedimentary rock-hosted stratiform copper district that contains significant cobalt. Its presence may indicate significant mafic-ultramafic rocks in the local basement. The balance of primary cobalt production is from magmatic nickel-copper and nickel laterite deposits. Cobalt is present in several carbonate-hosted lead-zinc and copper districts. It is also variably present in Besshi-type volcanogenic massive sulfide and siliciclastic sedimentary rock-hosted deposits in back arc and rift environments associated with mafic-ultramafic rocks. Metasedimentary cobalt-copper-gold deposits (such as Blackbird, Idaho), iron oxide-copper-gold deposits, and the five-element vein deposits (such as Cobalt, Ontario) contain different amounts of cobalt. None of these deposit types show direct links to mafic-ultramafic rocks; the deposits may result from crustal-scale hydrothermal systems capable of leaching and transporting cobalt from great depths. Hydrothermal deposits associated with ultramafic rocks, typified by the Bou Azzer district of Morocco, represent another type of primary cobalt deposit. In the United States, exploration for cobalt deposits may focus on magmatic nickel-copper deposits in the Archean and Proterozoic rocks of the Midwest and the east coast (Pennsylvania) and younger mafic rocks in southeastern and southern Alaska; also, possibly basement rocks in southeastern Missouri. Other potential exploration targets include— The Belt-Purcell basin of British Columbia (Canada), Idaho, Montana, and Washington for different styles of sedimentary rock-hosted cobalt deposits; Besshi-type VMS deposits, such as the Greens Creek (Alaska) deposit and the Ducktown (Tennessee) waste and tailings; and Known five-element vein districts in Arizona and New Mexico, as well as in the Yukon-Tanana terrane of Alaska; and hydrothermal deposits associated with ultramafic rocks along the west coast, in Alaska, and in the Appalachian Mountains.

Open-File Report↗
USGS2017

Mineral potential mapping in an accreted island-arc setting using aeromagnetic data: An example from southwest Alaska

The distribution of volcanogenic massive sulfide (VMS), porphyry-epithermal, Alaska-type ultramafic-mafic complexes, intrusion-related Au, and granitoid Sn-W ore deposits in southwest Alaska supports current metallogenic models linking the formation of these deposit types to the emplacement of different suites of igneous rocks during the evolution of this convergent plate margin. Regional-scale aeromagnetic data provide a continuous set of observations over the deposits and show contrasting patterns over the igneous rock suites hosting the various deposit types. Combined with surface geologic data and regional metallogenic constraints, aeromagnetic data—filtered to enhance the anomalous magnetic field and map magnetic domains—were used to produce a mineral potential map across this accreted island-arc setting. The reduced-to-pole, upward continuation, and total horizontal gradient transform maps show anomalies that could represent porphyry-epithermal deposits within the intraoceanic- and continental-arc terranes. The tilt derivative transform highlights lineaments within the back arc that may represent zones with potential for VMS deposits. The truncations of tilt derivative lineaments outline a major magnetic domain boundary between the back-arc and craton margin, which is prospective for granitoid Sn-W deposits. Annular tilt derivative highs outline granitoids that could be associated with intrusion-related Au deposits within the craton margin. Shallow, magnetite-rich Alaska-type ultramafic-mafic complexes are mapped by their short-wavelength, high-amplitude anomalies. Successful mineral potential mapping across southwestern Alaska as performed in the present study suggests that filtered aeromagnetic data can be effectively used in mineral exploration in convergent continental margin settings.

Alaska↗
USGS2016

Critical elements in sediment-hosted deposits (clastic-dominated Zn-Pb-Ag, Mississippi Valley-type Zn-Pb, sedimentary rock-hosted Stratiform Cu, and carbonate-hosted Polymetallic Deposits): A review: Chapter 12

Some sediment-hosted base metal deposits, specifically the clastic-dominated (CD) Zn-Pb deposits, carbonate-hosted Mississippi Valley-type (MVT) deposits, sedimentary-rock hosted stratiform copper deposits, and carbonate-hosted polymetallic (“Kipushi type”) deposits, are or have been important sources of critical elements including Co, Ga, Ge, and Re. The generally poor data concerning trace element concentrations in these types of sediment-hosted ores suggest that there may be economically important concentrations of critical elements yet to be recognized.

Book chapter↗
USGS2014

Three-dimensional distribution of igneous rocks near the Pebble porphyry Cu-Au-Mo deposit in southwestern Alaska: constraints from regional-scale aeromagnetic data

Aeromagnetic data helped us to understand the 3D distribution of plutonic rocks near the Pebble porphyry copper deposit in southwestern Alaska, USA. Magnetic susceptibility measurements showed that rocks in the Pebble district are more magnetic than rocks of comparable compositions in the Pike Creek–Stuyahok Hills volcano-plutonic complex. The reduced-to-pole transformation of the aeromagnetic data demonstrated that the older rocks in the Pebble district produce strong magnetic anomaly highs. The tilt derivative transformation highlighted northeast-trending lineaments attributed to Tertiary volcanic rocks. Multiscale edge detection delineated near-surface magnetic sources that are mostly outward dipping and coalesce at depth in the Pebble district. The total horizontal gradient of the 10-km upward-continued magnetic data showed an oval, deep magnetic contact along which porphyry deposits occur. Forward and inverse magnetic modeling showed that the magnetic rocks in the Pebble district extend to depths greater than 9 km. Magnetic inversion was constrained by a near-surface, 3D geologic model that is attributed with measured magnetic susceptibilities from various rock types in the region. The inversion results indicated that several near-surface magnetic sources with moderate susceptibilities converge with depth into magnetic bodies with higher susceptibilities. This deep magnetic source appeared to rise toward the surface in several areas. An isosurface value of 0.02 SI was used to depict the magnetic contact between outcropping granodiorite and nonmagnetic sedimentary host rocks. The contact was shown to be outward dipping. At depths around 5 km, nearly the entire model exceeded the isosurface value indicating the limits of nonmagnetic host material. The inversion results showed the presence of a relatively deep, northeast-trending magnetic low that parallels lineaments mapped by the tilt derivative. This deep low represents a strand of the Lake Clark fault.

Alaska↗
USGS2014

Sediment-hosted stratabound copper assessment of the Neoproterozoic Roan Group, central African copperbelt, Katanga Basin, Democratic Republic of the Congo and Zambia

This study estimates the location, quality, and quantity of undiscovered copper in stratabound deposits within the Neoproterozoic Roan Group of the Katanga Basin in the Democratic Republic of the Congo and Zambia. The study area encompasses the Central African Copperbelt, the greatest sediment-hosted copper-cobalt province in the world, containing 152 million metric tons of copper in greater than 80 deposits. This study (1) delineates permissive areas (tracts) where undiscovered sediment-hosted stratabound copper deposits may occur within 2 kilometers of the surface, (2) provides a database of known sediment-hosted stratabound copper deposits and prospects, (3) estimates numbers of undiscovered deposits within these permissive tracts at several levels of confidence, and (4) provides probabilistic estimates of amounts of copper and mineralized rock that could be contained in undiscovered deposits within each tract. The assessment, conducted in January 2010 using a three-part form of mineral resource assessment, indicates that a substantial amount of undiscovered copper resources might occur in sediment-hosted stratabound copper deposits within the Roan Group in the Katanga Basin. Monte Carlo simulation results that combine grade and tonnage models with estimates of undiscovered deposits indicate that the mean estimate of undiscovered copper in the study area is 168 million metric tons, which is slightly greater than the known resources at 152 million metric tons. Furthermore, significant value can be expected from associated metals, particularly cobalt. Tracts in the Democratic Republic of the Congo (DRC) have potential to contain near-surface, undiscovered deposits. Monte Carlo simulation results indicate a mean value of 37 million metric tons of undiscovered copper may be present in significant prospects.

Katanga Basin↗
USGS2013

Geological analysis of aeromagnetic data from southwestern Alaska: Implications for exploration in the area of the Pebble porphyry Cu-Au-Mo deposit

Aeromagnetic data are used to better understand the geology and mineral resources near the Late Cretaceous Pebble porphyry Cu-Au-Mo deposit in southwestern Alaska. The reduced-to-pole (RTP) transformation of regional-scale aeromagnetic data shows that the Pebble deposit is within a cluster of magnetic anomaly highs. Similar to Pebble, the Iliamna, Kijik, and Neacola porphyry copper occurrences are in magnetic highs that trend northeast along the crustal-scale Lake Clark fault. A high-amplitude, short- to moderate-wavelength anomaly is centered over the Kemuk occurrence, an Alaska-type ultramafic complex. Similar anomalies are found west and north of Kemuk. A moderate-amplitude, moderate-wavelength magnetic low surrounded by a moderate-amplitude, short-wavelength magnetic high is associated with the gold-bearing Shotgun intrusive complex. The RTP transformation of the district-scale aeromagnetic data acquired over Pebble permits differentiation of a variety of Jurassic to Tertiary magmatic rock suites. Jurassic-Cretaceous basalt and gabbro units and Late Cretaceous biotite pyroxenite and granodiorite rocks produce magnetic highs. Tertiary basalt units also produce magnetic highs, but appear to be volumetrically minor. Eocene monzonite units have associated magnetic lows. The RTP data do not suggest a magnetite-rich hydrothermal system at the Pebble deposit. The 10-km upward continuation transformation of the regional-scale data shows a linear northeast trend of magnetic anomaly highs. These anomalies are spatially correlated with Late Cretaceous igneous rocks and in the Pebble district are centered over the granodiorite rocks genetically related to porphyry copper systems. The spacing of these anomalies is similar to patterns shown by the numerous porphyry copper deposits in northern Chile. These anomalies are interpreted to reflect a Late Cretaceous magmatic arc that is favorable for additional discoveries of Late Cretaceous porphyry copper systems in southwestern Alaska.

Alaska↗
USGS2012

Sandstone copper assessment of the Chu-Sarysu Basin, Central Kazakhstan: Chapter E in Global mineral resource assessment

Mineral resource assessments represent a synthesis of available information to estimate the location, quality, and quantity of undiscovered mineral resources in the upper part of the Earth’s crust. This report presents a probabilistic mineral resource assessment of undiscovered sandstone copper deposits within the late Paleozoic Chu-Sarysu Basin in central Kazakhstan by the U.S. Geological Survey as a contribution to a global assessment of mineral resources. The purposes of this study are to: (1) provide a database of known sandstone copper deposits and significant prospects in this area, (2) delineate permissive areas (tracts) for undiscovered sandstone copper deposits within 2 km of the surface at a scale of 1:1,000,000, (3) estimate numbers of undiscovered deposits within these permissive tracts at several levels of confidence, and (4) provide probabilistic estimates of amounts of copper (Cu), silver (Ag), and mineralized rock that could be contained in undiscovered deposits within each tract. The assessment uses the three-part form of mineral resource assessment based on mineral deposit models (Singer, 1993; Singer and Menzie, 2010). Delineation of permissive tracts for resources is based on the distribution of a Carboniferous oxidized nonmarine clastic (red bed) stratigraphic sequence that lies between overlying Permian and underlying Devonian evaporite-bearing sequences. Subsurface information on the extent and depth of this red bed sequence and structural features that divide the basin into sub-basins was used to define four permissive tracts. Structure contour maps, mineral occurrence databases, drill hole lithologic logs, geophysical maps, soil geochemical maps, locations of producing gas fields, and evidence for former gas accumulations were considered in conjunction with descriptive deposit models and grade and tonnage models to guide the assessment team’s estimates of undiscovered deposits in each tract. The four permissive tracts are structural sub-basins of the Chu-Sarysu Basin and range in size from 750 to 65,000 km². Probabilistic estimates of numbers of undiscovered sandstone copper deposits were made for the four tracts by a group of experts. Using these probabilistic estimates, Monte Carlo simulation was used to estimate the amount of metal contained within each tract. The results of the simulation serve as the basis for estimates of the metal endowment. The team estimates that 26 undiscovered deposits occur within the Chu-Sarysu Basin, and that these deposits contain an arithmetic mean of at least 21.5 million metric tons (Mt) of copper and 21,900 metric tons (t) of silver. The undiscovered deposits are in addition to the 7 known deposits that contain identified resources of 27.6 Mt of copper. Sixty percent of the estimated mean undiscovered copper resources are associated with the two permissive tracts that contain the identified resources; the remaining estimated resources are associated with the two tracts that have no known deposits. For the three tracts that contain 95 percent of the estimated undiscovered copper resources, the probability that each tract contains its estimated mean or more is about 40 percent. For the tract with 5 percent of the estimated undiscovered cop-per resources, the probability that it contains that amount or more is 25 percent.

Chu-Sarysu Basin↗