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Frontier of the K–Ar (40Ar/39Ar) Geochronology
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Frontier of the K–Ar (40Ar/39Ar) Geochronology

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Geochemistry and Geochronology".

Deadline for manuscript submissions: closed (27 July 2022) | Viewed by 12179

Special Issue Editors

Dr. Tetsumaru Itaya

E-Mail Website
Guest Editor
Institute of GeoHistory, Japan Geochronology Network (NPO), Akaiwa 701-2503, Japan
Interests: K–Ar (40Ar/39Ar) geochronology; field geology; petrology; mineralogy; opaque mineralogy; graphitization
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Tatsuki Tsujimori

E-Mail Website
Guest Editor
Department of Earth Science, Tohoku University, Aoba Ku, Sendai, Miyagi 9808578, Japan
Interests: orogenic belts; HP-UHP metamorphism; blueschist; serpentinite; jadeitite
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Radiogenic 40Ar was discovered from natural minerals in 1948, and the K–Ar dating method has been developed since the 1950s. Subsequently, the 40Ar/39Ar dating method was established in the 1960s, and further developments in the application of the 40Ar/39Ar led to improvement of the in situ dating technique. Thus far, this K–Ar (40Ar/39Ar) method has been applied to many varieties of geological materials as the most approachable radiometric dating method. However, the method often yields some certain geological inconsistency and/or anomalously old ages, especially for high- and ultrahigh pressure (HP–UHP) metamorphic rocks in collisional orogenic belts. For example, some micas in UHP-metamorphosed granite give unusual apparent K–Ar (40Ar/39Ar) ages, significantly older than the host granite. Such observation infers the presence of extremely high excess argon. This problem has been discussed by many geochronologists for the last 40 years. Although the reconnaissance of radiogenic argon-loss or -gain is difficult, multidisciplinary approaches have the potential to understand the physicochemical behavior of argon in nature and to improve the reliability of K–Ar (40Ar/39Ar) dating of metamorphic processes.

Understanding argon behavior also enables more accurate K–Ar (40Ar/39Ar) dating for young volcanic rocks which have experienced Ar isotope mass fractionation and for fluid-induced gold mineralization with excess argon. Furthermore, it would improve authigenic illite and smectite K–Ar (40Ar/39Ar) dating for fault gouge rocks, which has been applied to determine fault movements.

This Special Issue invites submissions from K–Ar (40Ar/39Ar) geochronology and geochemistry within a multidisciplinary scope, including field observations, petrology, mineralogy, structural geology, and numerical modeling. Studies that help to better understand argon behavior in nature are particularly encouraged.

Prof. Dr. Tetsumaru Itaya
Prof. Dr. Tatsuki Tsujimori
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • K–Ar (40Ar/39Ar) geochronology
  • Excess argon and wave
  • Argon release by deformation
  • Exhumation of metamorphic units
  • Argon behavior in nature
  • Accurate and reliable dating

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Related Special Issue

Published Papers (5 papers)

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Research

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20 pages, 8236 KiB  
Article
In Situ Argon Isotope Analyses of Chondrule-Forming Materials in the Allende Meteorite: A Preliminary Study for 40Ar/39Ar Dating Based on Cosmogenic 39Ar
by Yuko Takeshima, Hironobu Hyodo, Tatsuki Tsujimori, Chitaro Gouzu and Tetsumaru Itaya
Minerals 2023, 13(1), 31; https://doi.org/10.3390/min13010031 - 25 Dec 2022
Cited by 1 | Viewed by 2387
Abstract
The argon isotopic compositions of chondrule-forming minerals of the Allende (CV3) meteorite were examined to evaluate the possibility of in situ 40Ar/39Ar dating of planetary surface rocks based on cosmogenic 39Ar without neutron irradiation in a reactor. The investigated [...] Read more.
The argon isotopic compositions of chondrule-forming minerals of the Allende (CV3) meteorite were examined to evaluate the possibility of in situ 40Ar/39Ar dating of planetary surface rocks based on cosmogenic 39Ar without neutron irradiation in a reactor. The investigated Allende meteorite sample (ME-247H: 50 mm × 45 mm × 5 mm; 28.85 g) contains at least three textural types of chondrules: barred olivine chondrule (BOC), porphyritic olivine chondrule (POC), and unclassified chondrule (UC). Most chondrules contain olivine, low-Ca pyroxene, clinopyroxene, and plagioclase as primary phases, with minor amounts of nepheline and sodalite formed during aqueous alteration of the CV3 parent body of the early solar system. In situ argon isotope analyses on selected chondrule-forming minerals in petrographic sections of two BOCs, two POCs, and one UC using a Nd:YAG pulse laser confirmed a significant amount of cosmogenic 39Ar that formed by a 39K (n, p) 39Ar reaction in an extraterrestrial environment. Laser step-heating analyses of five bulk chondrules irradiated in a reactor revealed a plateau age (3.32 ± 0.06 Ga) from one of the five chondrules. The age spectra of all chondrules show the younger age in the low-temperature fractions, resulting in the integrated ages from 2.7 to 3.2 Ga. These results suggest that the Allende meteorite experienced argon isotopic homogenization at 3.3 Ga and the argon loss in part after the 3.3 Ga. Apparent ages of chondrule-forming minerals that were calculated using the J values of nephelines in one BOC and two POCs do not show any consistent relationship among the three types of chondrules (BOC, POC, and UC). This might be attributed to the fact that the isotopic heterogeneity among minerals took place during the heterogeneous argon loss stage after the 3.3 Ga event. Full article
(This article belongs to the Special Issue Frontier of the K–Ar (40Ar/39Ar) Geochronology)
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24 pages, 12983 KiB  
Article
Metamorphic Ages of the Jurassic Accretionary Complexes in the Kanto Mountains, Central Japan, Determined by K–Ar Dating of Illite: Implications for the Tectonic Relationship between the Chichibu and Sanbagawa Belts
by Zhiqiang Lu, Ichiko Shimizu and Tetsumaru Itaya
Minerals 2022, 12(12), 1515; https://doi.org/10.3390/min12121515 - 27 Nov 2022
Cited by 2 | Viewed by 1704
Abstract
To determine the metamorphic ages of the accretionary complexes in the Northern Chichibu Belt in SW Japan, K–Ar dating was conducted using weakly metamorphosed sedimentary rocks collected from the Kanto Mountains, Central Japan. Whole-rock ages were obtained for chert and red shale samples, [...] Read more.
To determine the metamorphic ages of the accretionary complexes in the Northern Chichibu Belt in SW Japan, K–Ar dating was conducted using weakly metamorphosed sedimentary rocks collected from the Kanto Mountains, Central Japan. Whole-rock ages were obtained for chert and red shale samples, and the mineral ages of fine-grained illite with a grain size of less than 4 μm were obtained for chert, red shale, mudstone, acidic tuff, and basic tuff. The K–Ar ages of chert and red shale presented large variations, with systematically older ages compared to those of mudstone and tuff in the same strata. The influence of submarine hydrothermal activities on chert and red shale before subduction is a possible cause of this deviation. The illite samples, which were fractionated into four grain-size classes using a suspension method, yielded older ages and higher illite crystallinity (i.e., smaller values of Kübler’s crystallinity index) for larger grain-size classes. The peak metamorphic ages were determined from the K–Ar ages of the 3–4 μm class illite in mudstone and tuff. The Late Jurassic to the Earliest Cretaceous accretionary complex of the lowest structural unit (Kashiwagi Unit) was dated within a small range between 117–110 Ma, which is distinctly older than the K–Ar ages of white mica reported from the Sanbagawa Belt. The peak metamorphic age of acidic tuff (113 Ma) at the type locality of the Mikabu Greenstones indicates that the subducted Mikabu seamount is a constituent of the Kashiwagi Unit. The peak metamorphic ages of the Manba and Kamiyoshida Units were obtained as 132–107 Ma and 163–144 Ma, respectively. Major structural discontinuity is suggested within the Middle Jurassic accretionary complexes. Full article
(This article belongs to the Special Issue Frontier of the K–Ar (40Ar/39Ar) Geochronology)
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12 pages, 2916 KiB  
Article
Large Amount of Excess Argon in Hydrothermal Quartz from the Vangtat Orogenic Gold Belt, Southern Laos: New In-Sight from K-Ar and Noble Gas Isotope Analyses
by Patthana Bounliyong, Hirochika Sumino and Antonio Arribas
Minerals 2022, 12(10), 1205; https://doi.org/10.3390/min12101205 - 24 Sep 2022
Cited by 1 | Viewed by 1794
Abstract
K-Ar dating and 3He/4He and 40Ar/36Ar analyses were conducted on samples of hydrothermal quartz from the Thongkai-Ok Au deposit in the Vangtat orogenic Au belt of southern Laos to study the presence of excess argon in hydrothermal [...] Read more.
K-Ar dating and 3He/4He and 40Ar/36Ar analyses were conducted on samples of hydrothermal quartz from the Thongkai-Ok Au deposit in the Vangtat orogenic Au belt of southern Laos to study the presence of excess argon in hydrothermal quartz and to better understand the origin of the ore-forming fluids. The K-Ar age of two hydrothermal quartz separates yielded apparent dates of 1040 and 1385 Ma. These ages are significantly older than the estimated age of Vangtat Au mineralization (~200 Ma) and other regional geologic events, indicating the presence of an extraordinary amount of excess argon in the hydrothermal quartz crystals. In vacuo crushing analyses of the Thongkai-Ok hydrothermal vein quartz delivered 3He/4He ≈ 0.2–0.3 R/Ra and 40Ar/36Ar ≈ 455–725, suggesting the ore-forming fluid is mainly derived from a crustal component with a minor contribution of mantle and meteoric fluids. Full article
(This article belongs to the Special Issue Frontier of the K–Ar (40Ar/39Ar) Geochronology)
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77 pages, 39676 KiB  
Article
Formation of a Composite Albian–Eocene Orogenic Wedge in the Inner Western Carpathians: P–T Estimates and 40Ar/39Ar Geochronology from Structural Units
by Marián Putiš, Ondrej Nemec, Martin Danišík, Fred Jourdan, Ján Soták, Čestmír Tomek, Peter Ružička and Alexandra Molnárová
Minerals 2021, 11(9), 988; https://doi.org/10.3390/min11090988 - 9 Sep 2021
Cited by 8 | Viewed by 2531
Abstract
The composite Albian–Eocene orogenic wedge of the northern part of the Inner Western Carpathians (IWC) comprises the European Variscan basement with the Upper Carboniferous–Triassic cover and the Jurassic to Upper Cretaceous sedimentary successions of a large oceanic–continental Atlantic (Alpine) Tethys basin system. This [...] Read more.
The composite Albian–Eocene orogenic wedge of the northern part of the Inner Western Carpathians (IWC) comprises the European Variscan basement with the Upper Carboniferous–Triassic cover and the Jurassic to Upper Cretaceous sedimentary successions of a large oceanic–continental Atlantic (Alpine) Tethys basin system. This paper presents an updated evolutionary model for principal structural units of the orogenic wedge (i.e., Fatricum, Tatricum and Infratatricum) based on new and published white mica 40Ar/39Ar geochronology and P–T estimates by Perple_X modeling and geothermobarometry. The north-directed Cretaceous collision led to closure of the Jurassic–Early Cretaceous basins, and incorporation of their sedimentary infill and a thinned basement into the Albian–Cenomanian/Turonian accretionary wedge. During this compressional D1 stage, the subautochthonous Fatric structural units, including the present-day higher Infratatric nappes, achieved the metamorphic conditions of ca. 250–400 °C and 400–700 MPa. The collapse of the Albian–Cenomanian/Turonian wedge and contemporary southward Penninic oceanic subduction enhanced the extensional exhumation of the low-grade metamorphosed structural complexes (D2 stage) and the opening of a fore-arc basin. This basin hemipelagic Coniacian–Campanian Couches-Rouges type marls (C.R.) spread from the northern Tatric edge, throughout the Infratatric Belice Basin, up to the peri-Pieniny Klippen Belt Kysuca Basin, thus tracing the south-Penninic subduction. The ceasing subduction switched to the compressional regime recorded in the trench-like Belice “flysch” trough formation and the lower anchi-metamorphism of the C.R. at ca. 75–65 Ma (D3 stage). The Belice trough closure was followed by the thrusting of the exhumed low-grade metamorphosed higher Infratatric complexes and the anchi-metamorphosed C.R. over the frontal unmetamorphosed to lowest anchi-metamorphosed Upper Campanian–Maastrichtian “flysch” sediments at ca. 65–50 Ma (D4 stage). Phengite from the Infratatric marble sample SRB-1 and meta-marl sample HC-12 produced apparent 40Ar/39Ar step ages clustered around 90 Ma. A mixture interpretation of this age is consistent with the presence of an older metamorphic Ph1 related to the burial (D1) within the Albian–Cenomanian/Turonian accretionary wedge. On the contrary, a younger Ph2 is closely related to the late- to post-Campanian (D3) thrust fault formation over the C.R. Celadonite-enriched muscovite from the subautochthonous Fatric Zobor Nappe meta-quartzite sample ZI-3 yielded a mini-plateau age of 62.21 ± 0.31 Ma which coincides with the closing of the Infratatric foreland Belice “flysch” trough, the accretion of the Infratatricum to the Tatricum, and the formation of the rear subautochthonous Fatricum bivergent structure in the Eocene orogenic wedge. Full article
(This article belongs to the Special Issue Frontier of the K–Ar (40Ar/39Ar) Geochronology)
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Review

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14 pages, 1752 KiB  
Review
Illite-Age-Analysis (IAA) for the Dating of Shallow Faults: Prerequisites and Procedures for Improvement
by Yungoo Song and Ho Sim
Minerals 2021, 11(11), 1162; https://doi.org/10.3390/min11111162 - 21 Oct 2021
Cited by 3 | Viewed by 2070
Abstract
Fault age determination using the illite-age-analysis (IAA) method for fault gouges has played a key role in providing absolute age information in tectonic evolution studies for the last 20 years. The accuracy and precision of the IAA method depend on (1) how to [...] Read more.
Fault age determination using the illite-age-analysis (IAA) method for fault gouges has played a key role in providing absolute age information in tectonic evolution studies for the last 20 years. The accuracy and precision of the IAA method depend on (1) how to reasonably quantify the relative content of 1M/1Md illite generated from fault activity compared to detrital 2M1 illite in the size fractions of the fault gouge, and (2) how to minimize the error factors in K-Ar or Ar-Ar dating analysis. XRD-based quantitative analysis of illite polytype has made great progress in accuracy by generating a simulated XRD pattern of 1M/1Md polytype using WILDFIRE© and full-pattern-fitting it with the XRD pattern measured from size fractions of the fault gauge. Nevertheless, the results of quantitative analysis of illite polytypes may vary depending on the sample state of the size fractions for XRD analysis, especially the preferred orientation due to the layered crystal structure of illite. In addition, the radiometric dating results may be distorted depending on the error factor of the dating method itself and on the mineral composition of the size fractions, that is, the presence of K-containing minerals such as biotite and K-feldspar other than illite. In this study, we reviewed previous studies that determined fault activity ages by applying IAA to fault gouges. From this, the prerequisites and recommendations for each of the five steps (particle size separation process, XRD analysis process, polytype quantification, radiometric dating, IAA plot) for improving the IAA method are summarized and presented. The continuous application of the improved IAA is expected to greatly contribute to the study of tectonic evolution through geological time. Full article
(This article belongs to the Special Issue Frontier of the K–Ar (40Ar/39Ar) Geochronology)
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