scholarly journals Linking Mineralogy to Lithogeochemistry in the Highland Valley Copper District: Implications for Porphyry Copper Footprints

2020 ◽  
Vol 115 (4) ◽  
pp. 871-901 ◽  
Author(s):  
Kevin Byrne ◽  
Guillaume Lesage ◽  
Sarah A. Gleeson ◽  
Stephen J. Piercey ◽  
Philip Lypaczewski ◽  
...  
Keyword(s):  
Infrared Imaging ◽  
White Mica ◽  
Coarse Grained ◽  
Late Triassic ◽  
Material Transfer ◽  
Rock Composition ◽  
Porphyry Cu ◽  
Propylitic Alteration ◽  
Shortwave Infrared ◽  
Pathfinder Elements

Abstract The Highland Valley Copper porphyry deposits, hosted in the Late Triassic Guichon Creek batholith in the Canadian Cordillera, are unusual in that some of them formed at depths of at least 4 to 5 km in cogenetic host rocks. Enrichments in ore and pathfinder elements are generally limited to a few hundred meters beyond the pit areas, and the peripheral alteration is restricted to narrow (1–3 cm) halos around a low density of prehnite and/or epidote veinlets. It is, therefore, challenging to recognize the alteration footprint peripheral to the porphyry Cu systems. Here, we document a workflow to maximize the use of lithogeochemical data in measuring changes in mineralogy and material transfer related to porphyry formation by linking whole-rock analyses to observed alteration mineralogy at the hand specimen and deposit scale. Alteration facies and domains were determined from mapping, feldspar staining, and shortwave infrared imaging and include (1) K-feldspar halos (potassic alteration), (2) epidote veins with K-feldspar–destructive albite halos (sodic-calcic alteration), (3) quartz and coarse-grained muscovite veins and halos and fine-grained white-mica–chlorite veins and halos (white-mica–chlorite alteration), and two subfacies of propylitic alteration comprising (4) prehnite veinlets with white-mica–chlorite-prehnite halos, and (5) veins of epidote ± prehnite with halos of chlorite and patchy K-feldspar. Well-developed, feldspar-destructive, white-mica alteration is indicated by (2[Ca-C] + N + K)/Al values <0.85, depletion in CaO and Na2O, enrichment in K2O, and localized SiO2 addition and is spatially limited to within ~200 m of porphyry Cu mineralization. Localized K2O, Fe2O3, and depletion in Cu, and some enrichment in Na2O and CaO, occurs in sodic-calcic domains that form a large (~34 km2) nonconcentric footprint outboard of well-mineralized and proximal zones enriched in K. Water and magmatic CO2-rich propylitic and sodic-calcic–altered rocks form the largest lithogeochemical footprint to the mineralization in the Highland Valley Copper district (~60 km2). Calcite in the footprint is interpreted to have formed via phase separation of CO2 from a late-stage magmatic volatile phase. Several observations from this study are transferable to other porphyry systems and have implications for porphyry Cu exploration. Feldspar staining and shortwave infrared imaging highlight weak and cryptic alteration that did not cause sufficient material transfer to be confidently distinguished from protolith lithogeochemical compositions. Prehnite can be a key mineral phase in propylitic alteration related to porphyry genesis, and its presence can be predicted based on host-rock composition. Sodic-calcic alteration depletes the protolith in Fe (and magnetite) and, therefore, will impact petrophysical and geophysical characteristics of the system. Whole-rock loss on ignition and C and S analyses can be used to map enrichment in water and CO2 in altered rocks, and together these form a large porphyry footprint that extends beyond domains of enrichment in ore and pathfinder elements and of pronounced alkali metasomatism.

scholarly journals Characterization of Mineralogy in the Highland Valley Porphyry Cu District Using Hyperspectral Imaging, and Potential Applications

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 473
Author(s):  
Philip Lypaczewski ◽  
Benoit Rivard ◽  
Guillaume Lesage ◽  
Kevin Byrne ◽  
Michael D’Angelo ◽  
...  
Keyword(s):  
High Spatial Resolution ◽  
White Mica ◽  
Coarse Grained ◽  
Drill Core ◽  
Production Environment ◽  
Rock Samples ◽  
Porphyry Cu ◽  
Potential Applications ◽  
Shortwave Infrared

The Highland Valley Copper (HVC) district in British Columbia, Canada, is host to at least four major porphyry Cu systems: Bethlehem (~209 Ma), and Valley, Lornex, and Highmont (~208 to 207 Ma). High spatial resolution (0.2–1.0 mm/pixel) hyperspectral imagery in the shortwave infrared (SWIR) were acquired on 755 rock samples and 400 m of continuous drill core. Spectral metrics are used to measure the relative abundance of 12 minerals and an additional metric is derived to estimate white mica grain size. In the Valley and Lornex deposits, coarse-grained white mica is associated with mineralization and is detectable up to 4 km away from the deposits. Kaolinite is present within 2 km of the mineralized centers but does not necessarily occur within strongly mineralized intervals. Prehnite is ubiquitous from 4 to 8 km from the deposits. In the Bethlehem deposit, tourmaline and epidote are associated with mineralization. We propose a spectral alteration score based on these proximal hyperspectral SWIR mineralogical patterns to assist explorers in targeting porphyry Cu systems when using drill core, surface rock samples and potentially remote sensing imagery. In a production environment, this metric could serve to facilitate ore-sorting.

Mineralogical and Isotopic Characteristics of Sodic-Calcic Alteration in the Highland Valley Copper District, British Columbia, Canada: Implications for Fluid Sources in Porphyry Cu Systems

2020 ◽  
Vol 115 (4) ◽  
pp. 841-870 ◽  
Author(s):  
Kevin Byrne ◽  
Robert B. Trumbull ◽  
Guillaume Lesage ◽  
Sarah A. Gleeson ◽  
John Ryan ◽  
...  
Keyword(s):  
Water Source ◽  
White Mica ◽  
Late Triassic ◽  
Supporting Evidence ◽  
Fine Grained ◽  
Porphyry Cu ◽  
Mineral Assemblages ◽  
Alteration Minerals ◽  
External Water ◽  
Host Rocks

Abstract The Highland Valley Copper porphyry Cu (±Mo) district is hosted in the Late Triassic Guichon Creek batholith in the Canadian Cordillera. Fracture-controlled sodic-calcic alteration is important because it forms a large footprint (34 km2) outside of the porphyry Cu centers. This alteration consists of epidote ± actinolite ± tourmaline veins with halos of K-feldspar–destructive albite (1–20 XAn) ± fine-grained white mica ± epidote. The distribution of sodic-calcic alteration is strongly influenced by near-orthogonal NE- and SE-trending fracture sets and by proximity to granodiorite stocks and porphyry dikes. Multiple stages of sodic-calcic alteration occurred in the district, which both pre- and postdate Cu mineralization at the porphyry centers. The mineral assemblages and chemical composition of alteration minerals suggest that the fluid that caused sodic-calcic alteration in the Guichon Creek batholith was Cl bearing, at near-neutral pH, and oxidized, and had high activities of Na, Ca, and Mg relative to propylitic and fresh-rock assemblages. The metasomatic exchange of K for Na, localized removal of Fe and Cu, and a paucity of secondary quartz suggest that the fluid was thermally prograding in response to magmatic heating. Calculated δ18Ofluid and δDfluid values of mineral pairs in isotopic equilibrium from the sodic-calcic veins and alteration range from 4 to 8‰ and −20 to −9‰, respectively, which contrasts with the whole-rock values for least altered magmatic host rocks (δ18O = 6.4–9.4‰ and δD = −99 to −75‰). The whole-rock values are suggested to reflect residual magma values after D loss by magma degassing, while the range of hydrothermal minerals requires a mixed-fluid origin with a contribution of magmatic water and an external water source. The O-H isotope results favor seawater as the source but could also reflect the ingress of Late Triassic meteoric water. The 87Sr/86Srinital values of strongly Na-Ca–altered rocks range from 0.703416 to 0.703508, which is only slightly higher than the values of fresh and potassic-altered rocks. Modeling of those data suggests the Sr is derived predominantly from a magmatic source, but the system may contain up to 3% seawater Sr. Supporting evidence for a seawater-derived fluid entrained in the porphyry Cu systems comes from boron isotope data. The calculated tourmaline δ11Bfluid values from the sodic-calcic domains reach 18.3‰, which is consistent with a seawater-derived fluid source. Lower tourmaline δ11Bfluid values from the other alteration facies (4–10‰) suggest mixing between magmatic and seawater-derived fluids in and around the porphyry centers. These results imply that seawater-derived fluids can infiltrate batholiths and porphyry systems at deep levels (4–5 km) in the crust. Sodic ± calcic alteration may be more common in rocks peripheral to porphyry Cu systems hosted in island-arc terranes and submarine rocks than currently recognized.

Alteration Mineralogy of the Zhengguang Epithermal Au-Zn Deposit, Northeast China: Interpretation of Shortwave Infrared Analyses During Mineral Exploration and Assessment

2020 ◽  
Author(s):  
Le Wang ◽  
Jeanne B. Percival ◽  
Jeffrey W. Hedenquist ◽  
Keiko Hattori ◽  
Kezhang Qin
Keyword(s):  
Northeast China ◽  
Mineral Exploration ◽  
White Mica ◽  
Absorption Feature ◽  
Hydrous Minerals ◽  
Propylitic Alteration ◽  
Identification Software ◽  
Shortwave Infrared ◽  
Host Rocks ◽  
Epithermal Au

Abstract Alteration mineralogy from shortwave infrared (SWIR) spectroscopy was compared with X-ray diffraction (XRD) analyses for samples from the Zhengguang intermediate sulfidation epithermal Au-Zn deposit, eastern Central Asian orogenic belt, northeast China. The SWIR and XRD analyses indicate that alteration minerals in the vein-adjacent halo mainly comprise quartz, illite, and locally pyrite (QIP) and chlorite, whereas samples from the pervasive propylitic alteration of host basaltic andesite lava contain epidote, chlorite, carbonate, montmorillonite, and locally illite. SWIR mineral identifications from automated mineral identification software may not always be accurate; thus, the results should be validated by the user. The wavelength position of the Al-OH (~2,200 nm; wAlOH) absorption feature can be used to approximate the composition of illite or white mica. However, caution is required when using the wAlOH value to assess paleotemperatures, as the composition of illite can be influenced by the composition of the host rocks or the hydrothermal fluid. In addition, values of the illite spectral maturity (ISM; ratio of the depth of the ~2,200 nm minima divided by the ~1,900 nm minima) can be affected by the presence of other hydrous minerals, quartz-sulfide veins, and absorption intensity (which can be a function of rock coloration). Despite these cautions, the spatial distribution and variation of the wAlOH and ISM values for illite suggest that the high paleotemperature hydrothermal upflow zones related to the Zhengguang Au-Zn deposit were located below ore zones I and IV, which are predicted to be proximal to the intrusive center of the system.

Protracted Magmatism and Mineralized Hydrothermal Activity at the Gibraltar Porphyry Copper-Molybdenum Deposit, British Columbia

2020 ◽  
Vol 115 (5) ◽  
pp. 1119-1136 ◽  
Author(s):  
Christopher Kobylinski ◽  
Keiko Hattori ◽  
Scott Smith ◽  
Alain Plouffe
Keyword(s):  
Mineral Exploration ◽  
Porphyry Copper ◽  
Hydrothermal Activity ◽  
White Mica ◽  
Late Triassic ◽  
American Continent ◽  
North American Continent ◽  
Porphyry Cu ◽  
The North ◽  
Molybdenum Deposit

Abstract The Gibraltar Cu-Mo deposit, with a total tonnage of 3.2 million tons (Mt) Cu, is located in the Canadian Cordillera and hosted by the Late Triassic Granite Mountain batholith. The batholith formed through multiple intrusions of tonalitic rocks over a period of ~25 m.y. beginning at 229.2 ± 4.4 Ma in the Quesnel island arc before the accretion of the arc to the North American continent. Late in its evolution, Cu fertile magmas intruded in the center of the batholith, during at least three events from 218.9 ± 3.1 to 205.8 ± 2.1 Ma. The fertile magmas were hotter and more mafic than older barren magmas. They generated magmatic-hydrothermal activity, forming potassic alteration and white mica alteration, and produced Cu mineralization as chalcopyrite-quartz veinlets and disseminated chalcopyrite. Zircon in the Cu-bearing tonalite intrusion (218.9 ± 3.1 Ma) shows high Ce4+/Ce3+ (681 ± 286 [2σ], n =15) compared to those from older barren intrusions (129 ± 56 [2σ], n = 118). Oxidation conditions for parental magmas are calculated using the compositions of zircon and amphibole. The magmas for Cu-bearing intrusions have an average of fayalite-magnetite-quartz buffer (FMQ) +1.7 ± 0.7 (2σ, n = 73), whereas those for older barren intrusions have slightly lower fO2 (avg FMQ +1.3 ± 0.5 [2σ], n = 108), although the values are overlapping for the two. The bulk rocks of Cu-bearing tonalite intrusions in the Granite Mountain batholith have low Sr/Y ratios (<22) independent of the degrees of alteration. The low ratios are also reflected by low Sr/Y in zircon, suggesting that the low Sr/Y ratios of bulk rocks represent those of unaltered rocks. The values are low compared to those associated with many other porphyry Cu deposits globally. The data suggest that igneous rocks elsewhere with low Sr/Y in bulk rocks may have a potential to host economic Cu deposits. Ratios of Ce/Nd and Ce/Ce* (=Ce/((NdN)2SmN)) in zircon are positively correlated with the Ce4+/Ce3+ in zircon from the Granite Mountain batholith. Since the former two ratios can be obtained solely from zircon composition, these ratios from detrital zircon may be useful in evaluating the occurrences of oxidized intrusions in regional mineral exploration.

Impact of speckle on laser range-gated shortwave infrared imaging system target identification performance

2002 ◽  
Author(s):  
Ronald G. Driggers ◽  
Richard H. Vollmerhausen ◽  
Nicole M. Devitt ◽  
Carl E. Halford ◽  
Kenneth J. Barnard
Keyword(s):  
Infrared Imaging ◽  
Imaging System ◽  
Target Identification ◽  
Identification Performance ◽  
Laser Range ◽  
Infrared Imaging System ◽  
Shortwave Infrared

scholarly journals Shortwave Infrared Imaging with J-Aggregates Stabilized in Hollow Mesoporous Silica Nanoparticles

2018 ◽  
Author(s):  
Wei Chen ◽  
ChiAn Cheng ◽  
Emily Cosco ◽  
Shyam Ramakrishnan ◽  
Jakob Lingg ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Contrast Agents ◽  
Silica Nanoparticles ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Mesoporous Silica Nanoparticles ◽  
J Aggregates ◽  
Hollow Mesoporous Silica ◽  
Shortwave Infrared

Tissue is translucent to shortwave infrared (SWIR) light, rendering optical imaging superior in this region. However, the widespread use of optical SWIR imaging has been limited, in part, by the lack of bright, biocompatible contrast agents that absorb and emit light above 1000 nm. J-aggregation offers a means to transform stable, near-infrared (NIR) fluorophores into red-shifted SWIR contrast agents. Here we demonstrate that hollow mesoporous silica nanoparticles (HMSNs) can template the J-aggregation of NIR fluorophore IR-140 to result in nanomaterials that absorb and emit SWIR light. The J-aggregates inside PEGylated HMSNs are stable for multiple weeks in buffer and enable high resolution imaging <i>in vivo</i>with 980 nm excitation.

scholarly journals Surface chemistry-mediated metal nanoclusters for in vivo shortwave infrared imaging

2021 ◽  
Author(s):  
Xavier Le Guevel ◽  
Benjamin Musnier ◽  
Karl D. Wegner ◽  
Maxime Henry ◽  
Agnes Desroches-Castan ◽  
...  
Keyword(s):  
Surface Chemistry ◽  
Infrared Imaging ◽  
Metal Nanoclusters ◽  
Shortwave Infrared

Optical Design of Spaceborne Shortwave Infrared Imaging Spectrometer with Wide Field of View

2011 ◽  
Vol 40 (5) ◽  
pp. 673-678
Author(s):  
薛庆生 XUE Qing-sheng ◽  
林冠宇 LIN Guang-yu ◽  
宋克非 SONG Ke-fei
Keyword(s):  
Infrared Imaging ◽  
Optical Design ◽  
Field Of View ◽  
Wide Field ◽  
Imaging Spectrometer ◽  
Wide Field Of View ◽  
Shortwave Infrared

Analysis and Suppression of Stray Radiation of Shortwave Infrared Imaging System

2015 ◽  
Vol 52 (12) ◽  
pp. 122901 ◽  
Author(s):  
任国栋 Ren Guodong ◽  
张良 Zhang Liang ◽  
兰卫华 Lan Weihua ◽  
赵延 Zhao Yan ◽  
潘晓东 Pan Xiaodong
Keyword(s):  
Infrared Imaging ◽  
Imaging System ◽  
Infrared Imaging System ◽  
Stray Radiation ◽  
Shortwave Infrared

K–Ar age determinations on the fine fractions of clay mineral ‘Crystallinity Index Standards’ from the Palaeozoic mudrocks of southwest England

Clay Minerals ◽  
2019 ◽  
Vol 54 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Anna C. Schomberg ◽  
Klaus Wemmer ◽  
Laurence N. Warr ◽  
Georg H. Grathoff
Keyword(s):  
Clay Mineral ◽  
Crystallinity Index ◽  
White Mica ◽  
Early Jurassic ◽  
Late Triassic ◽  
X Ray Diffraction ◽  
Middle Ordovician ◽  
Late Cambrian ◽  
Isotopic Analyses ◽  
Mineral Crystallinity

AbstractClay mineral ‘Crystallinity Index Standards’ (CIS) composed of Palaeozoic mudrocks from southwest England were investigated systematically in five sub-fractions per sample for the first time. X-ray diffraction was used to determine mineral assemblages, calibrated 001 illite full-width-at-half-maximum (FWHM) values and illite polytype compositions, in addition to K–Ar isotopic analyses of all fine fractions. The FWHM results of the <2 µm fraction are consistent with previous studies and reflect the range of diagenetic to epizonal grades covered by the sample set SW1 to SW7 (~0.61–0.26°2θ). Diagenetic and lower anchizone samples also show significant broadening of 001 illite reflections in the finer fractions and contain mixtures of authigenic 1M + 1Md illite and detrital 2M1 white mica polytypes suitable for illite age analysis. The estimated end-member ages of the Bude (SW1-1992) and younger Crackington (SW3-2000) mudstones yield detrital ages of Late Cambrian to Middle Ordovician (493–457 Ma) and a broad range of 1M + 1Md illite ages between Middle Permian and Early Jurassic (271–190 Ma). The detrital age of the stratigraphically older Crackington Formation mudrock (SW2-1992) is Late Devonian (384–364 Ma) with 1M + 1Md illite ages between Late Triassic and Early Jurassic (219–176 Ma). The origin of Mesozoic 1M + 1Md illite ages may represent neocrystallized illite associated with Mesozoic hydrothermal events or similar events that thermally reset older authigenic illite with partial loss of radiogenic argon and no renewed crystal growth. In contrast, upper anchizonal and epizonal Devonian slates (SW3-2012, SW4-1992, SW6-1992 and SW7-2012) contain only the 2M1 polytype, with K–Ar ages younger than the stratigraphic age. The three finest fractions of SW4-1992 yield consistent Late Carboniferous ages (331–304 ± 7 Ma) that are considered to date the neocrystallized 2M1 mica. Most fractions of epizonal slate (SW6-1992, SW7-2012) yield Early Permian ages (293.6–273 Ma) corresponding to published cooling ages of the Tintagel High-Strain Zone and the intrusion of the Bodmin granite (291.4 ± 0.8 Ma). These first K–Ar age constraints for the fine fractions of the CIS should provide useful reference values for testing analytical procedures of illite age analysis.

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