Results of 40Ar/39Ar Dating of Ores of the Ermakovo F–Be Deposit,West Transbaikalia,Russia

Doklady Earth Sciences - The Ermakovo F–Be deposit, the largest Be deposit in Russia and one of the world’s largest deposits, is located in West Transbaikalia. The ores of the deposit...     

^40 Ar/^39 Ar Dating of the Shaxi Porphyry Cu-Au Deposit in the Southern Tan-Lu Fault Zone, Anhui Province

Four samples of plagioclase and biotite from the Shaxi porphyry in the lower part of the Yangtze metallogenic belt were analyzed for age determination with the 40Ar/39Ar method. The results yield reproducible ages of 126 Ma to 135 Ma with a high level of confidence according to the agreement between isochron and plateau ages. The four Ar-Ar ages are relatively consistent within the analytical error. These ages are also consistent with, but more precise than, previous K-Ar and Rb-Sr ages and thus provide better constraints on the time of porphyry formation and associated Cu-Au mineralization along the middle to lower part of the Yangtze metaliogenic belt. The ages of 126 to 135 Ma are interpreted to represent the intrusive time of the Shaxi porphyry, so that the Cu-Au mineralization should have occurred later due to the post-magmatic hydrothermal event.     

Y–REE Mineralization in Biotite–Arfvedsonite Granites of the Katugin Rare-Metal Deposit,Transbaikalia, Russia

Doklady Earth Sciences - This paper reports on the results of studies of the carbonate–fluoride isolations with extremely high Y and REE concentrations from biotite–arfvedsonite granite...     

Mineralogy of Precious Metals in Ores of the Biksizak Base–Metal Deposit,South Urals,Russia

Geology of Ore Deposits - Gold and silver mineralogy is studied in ores of the Biksizak base-metal deposit (South Urals, Russia). This is a skarn-related carbonate replacement mineralization...     

40Ar/39Ar Age of the Burinda Gold–Silver Deposit and Its Relationship to Magmatism (Northeastern Part of the Argun Superterrane)

Doklady Earth Sciences - Our investigations have made it possible to estimate the age of hydrothermal ore metasomatic rocks at the Burinda Au–Ag deposit, one of the best known in East Asia,...     

The Nature of Tungstenite of the Bystrinskoe Porphyry-Skarn Au–Fe–Cu Deposit (Eastern Transbaikalia,Russia)

Doklady Earth Sciences - Tungstenite of unusual shapes (spheroids, rings, threads, spirals, etc.) was found in scheelite of gold-bearing quartz–carbonate–pyrite–chalcopyrite...     

The Ni–Antimonide Mineral Assemblage: A Product of Recrystallization of Sn–Pb–Zn Ores of the Yuzhnoe Deposit,Sikhote-Alin,Russia

Doklady Earth Sciences - A mineral assemblage with nisbite NiSb2 and breithauptite NiSb unique for a Mesozoic (Sn)–Pb–Zn vein deposit is found during mineralogical–geochemical...     

Thermochronology of the Angara–Vitim Granitoid Batholith,Transbaikalia, Russia

Doklady Earth Sciences - We reconstructed the history of the Angara–Vitim batholith (AVB), characterized by the formation of huge volumes of granitic magma using thermochronological analysis...     

40Ar/39Ar Dating of Xuebaoding Granite in the Songpan-Garzê Orogenic Belt, Southwest China, and its Geological Significance

<正>Thus far,our understanding of the emplacement of Xuebaoding granite and the occurrence and evolution of the Songpan-Garze Orogenic Belt has been complicated by differing age spectra results.Therefore,in this study,the ~(40)Ar/~(39)Ar and sensitive high resolution ion micro-probe(SHRIMP) U-Pb dating methods were both used and the results compared,particularly with respect to dating data for Pankou and Pukouling granites from Xuebaoding,to establish ages that are close to the real emplacements.The results of SHRIMP U-Pb dating for zircon showed a high amount of U,but a very low value for Th/U.The high U amount,coupled with characteristics of inclusions in zircons,indicates that Xuebaoding granites are not suitable for U-Pb dating.Therefore,muscovite in the same granite samples was selected for ~(40)Ar/~(39)Ar dating.The ~(40)Ar/~(39)Ar age spectrum obtained on bulk muscovite from Pukouling granite in the Xuebaoding,gave a plateau age of 200.1±1.2 Ma and an inverse isochron age of 200.6±1.2 Ma.The ~(40)Ar/~(39)Ar age spectrum obtained on bulk muscovite from Pankou granite in the Xuebaoding gave another plateau age of 193.4±1.1 Ma and an inverse isochron age of 193.7±1.1 Ma. The ~(40)Ar/~(36)Ar intercept of 277.0±23.4(2σ) was very close to the air ratio,indicating that no apparent excess argon contamination was present.These age dating spectra indicate that both granites were emplaced at 200.6±1.3 Ma and 193.7±1.1 Ma,respectively.Through comparison of both dating methods and their results,we can conclude that it is feasible that the muscovite in the granite bearing high U could be used for ~(40)Ar/~(39)Ar dating without extra Ar.Based on this evidence,as well as the geological characteristics of the Xuebaoding W-Sn-Be deposit and petrology of granites,it can be concluded that the material origin of the Xuebaoding W-Sn-Be deposit might partially originate from the Xuebaoding granite group emplacement at about 200 Ma.Moreover,compared with other granites and deposits distributed in various positions in the Songpan-Garze Orogenic Belt,the Xuebaoding emplacement ages further show that the main rare metal deposits and granites in peripheral regions occurred earlier than those in the inner Songpan-Garze.Therefore,~(40)Ar/~(39)Ar dating of Xuebaoding granite will lay a solid foundation for studying the occurrence and evolution of granite and rare earth element deposits in the Songpan-Garze Orogenic Belt.     

Stratigraphy of the Okhotsk–Chukotka Belt in the Headwaters of the Malyi Anyui River (the Vicinity of Kupol Deposit): U–Pb and 40Ar/39Ar Age Data

Doklady Earth Sciences - U–Pb and 40Ar/39Ar age data obtained for volcanic rocks of the Okhotsk–Chukotka Belt in the headwaters of the Malyi Anyui River (the vicinity of Kupol deposit)...     

Occurrences of Excess ^40Ar in Hydrothermal Tourmaline： Interpretations from ^40 Ar-^39Ar Dating Results by Stepwise Heating

The occurrences of excess ^40Ar within a hydrothermal tourmaline is discussed in term of the analysis data of syngenetic muscovite and tourmaline from the Lushui hydrothermal tin-tungsten deposit in western Yunnan, China, using the ^40Ar-^39Ar stepwise heating technique. About 80% excess ^40 Ar was released in the last step when the tourmaline was fused, corresponding to a release of only -3% ^39 Ar （K）, which indicates that most excess ^40 Ar was held in the mineral lattice rather than in the channels parallel to the Z-axis. This suggests that the excess ^40 Ar was incorporated during crystallization and not diffused into the tourmaline during the post-crystallization history.     

Coupled Dissolution–Precipitation Reactions of Tennantite–Tetrahedrite Minerals in the Darasun Gold Deposit (Eastern Transbaikalia,Russia)

Geology of Ore Deposits - Heterogeneous rhythmic–zonal aggregates of tennantite-IV partly or completely replacing early homogeneous Zn-tetrahedrite-I grains and euhedral...     

Jurassic cooling ages in Paleozoic to early Mesozoic granitoids of northeastern Patagonia: 40Ar/39Ar, 40K–40Ar mica and U–Pb zircon evidence

International Journal of Earth Sciences - U–Pb SHRIMP zircon crystallization ages and Ar–Ar and K–Ar mica cooling ages for basement rocks of the Yaminué and Nahuel Niyeu...     

Mineral Phases of the Pd–Bi–Se System in the Ores at the Chudnoe Au–Pd Deposit (Subpolar Urals,Russia)

Doklady Earth Sciences - In the Pd–Bi–Se system, the only known mineral containing all three elements is padmaite PdBiSe. Three compounds with different element ratios have been found...     

Late Palaeozoic mineralization and tectonic evolution of the West Junggar metallogenic belt,Central Asia: constraints from Re–Os and 40Ar/39Ar geochronology

ABSTRACT

The West Junggar Metallogenic Belt (WJMB) is located between the Tianshan fault system and the Ertix fault system in the western part of the Central Asian Metallogenic Domain (CAMD). The belt features widespread late Palaeozoic granitic plutons, strike-slip faults, and porphyry copper and orogenic gold deposits. We collected nine molybdenite samples from the Baogutu III–IV Cu–Mo deposit and the Suyunhe Mo–W deposit, and 12 granitoid samples from the Jiaman, Kangde, Kulumusu, Bieluagaxi, Hatu, Akbastau, Miaoergou, Baogutu, Karamay, and Hongshan plutons in the WJMB. Molybdenite Re–Os dating gives metallogenesis ages of 312.7 and 299.7 Ma for the Baogutu III–IV and Suyunhe deposits, respectively. ⁴⁰Ar/³⁹Ar thermochronology yields biotite ages ranging from 326 to 302 Ma and K-feldspar ages from 297 to 264 Ma, indicating a regional medium-temperature cooling history in the WJMB during the late Carboniferous to middle Permian. By integrating these data with previous zircon U–Pb, amphibole ⁴⁰Ar/³⁹Ar, and zircon and apatite fission-track ages, we reconstruct the whole thermal history of the WJMB, which includes late Palaeozoic intrusive magmatism, porphyry Cu and W–Mo mineralization, and late Mesozoic tectonic uplift and exhumation of the WJMB. The regional ⁴⁰Ar/³⁹Ar cooling ages are consistent with the timing of regional sinistral strike-slip faulting, thereby indicating the tectonic significance of the cooling ages. We suggest that the biotite ⁴⁰Ar/³⁹Ar ages represent the static cooling of the granitic plutons after emplacement, since the ages are consistent with the U–Pb ages of the plutons. Thereafter, the oldest K-feldspar ⁴⁰Ar/³⁹Ar age may record the initiation of sinistral strike-slip movement on the Darabut, Mayile, and Baerluke faults. The regional faulting resulted in significant uplift of the WJMB during the early and middle Permian.     

The First Data of U/Pb and 40Ar/39Ar Dating of the Pre-Dzhugdzhur Volcanics: New Evidence of Time Diversity in the Formation of Individual Sectors of the Okhotsk–Chukotka Volcanogenic Belt

Doklady Earth Sciences - The first data of U/Pb and 40Ar/39Ar dating of volcanogenic rocks of the Pre-Dzhugdzhur volcano-tectonic trough (PDVT) of the Okhotsk–Chukotka volcanogenic belt...     

Pyrrhotite–Nisbite–Breithauptite–Sulfoantimonide Micromineral Assemblage: a Product of High-Temperature Recrystallization of Ores at the Yuzhnoe Vein-Type Tin–Silver–Polymetallic Deposit,Sikhote-Alin,Russia

Geology of Ore Deposits - Abstract—The paper presents the results of mineralogical studies of tin–silver–polymetallic ores localized at the deep level (500–700 m below the...     

A Reappraisal of the 40Ar/38Ar Dating Technique via Irradiation with γ-Rays

In a reconnaissance study, we investigated the potential of γ-ray induced production of ³⁸Ar_K from ³⁹K for geochronological applications. For this purpose, various age monitors commonly in use for the established ⁴⁰Ar/³⁹Ar-method were co-irradiated for 60 h at 17.6 MeV maximum energy in the ELBE facility, Dresden-Rossendorf, Germany. Because the available energy was low, total production of ³⁸Ar_K was depressed, leading to low J₃₈-values of (2.1–4.1) × 10^-6 and hence resulted in only minor ³⁸Ar excess when compared with atmospheric ³⁸Ar_/³⁶Ar ratios. In spite of these restrictions, ages of younger monitors could be reproduced within error, whereas older age reference materials showed discrepancies due to the low production rate. We observed Ca-derived contributions on ³⁶Ar in analysed CaF₂ reference materials, and calculated a limit for Ca-interference on ³⁸Ar_Ca of (³⁸Ar/³⁶Ar)_Ca = 0.07 ± 0.03 (1s). In addition, we investigated a potential recoil redistribution of ³⁸Ar by stepwise heating experiments, but could not quantify this further because of concurring processes. More work at higher photon energies is necessary to resolve other open issues, in particular the potential of utilising ⁴⁰Ar/³⁷Ar ratios for age determination and the possibility of ⁴²Ar production from ⁴⁴Ca, which would allow correction for Ca-interference reactions on other Ar isotopes. This would be a pre-requisite for dating extra-terrestrial rocks.     

Post-Ore Processes of Uranium Migration in the Sandstone-Hosted Type Deposits: 234U/238U, 238U/235U and U–Pb Systematics of Ores of the Namaru Deposit,Vitim District,Northern Transbaikalia

Geology of Ore Deposits - To assess the nature of the post-ore behaviour of uranium in the Namaru deposit (Khiagda ore field), U–Pb isotope systems and the isotopic composition of uranium...