Mineralogy and geochemistry of chloritholites from the Nepryakhino gold field, South Urals

Mapping Intimacies ◽

10.35597/2313-545x-2020-6-3-1 ◽

2020 ◽

pp. 3-15

Author(s):

V.V. Murzin ◽

D.A. Varlamov

Keyword(s):

Trace Element ◽

Fault Zone ◽

Mineral Assemblage ◽

Trace Element Composition ◽

Element Composition ◽

South Urals ◽

Gold Placer ◽

Accessory Minerals ◽

Gold Bearing

The chlorite rocks (chloritolites) exposed in a bedrock of the Mokhovoe boloto (Moss swamp) gold placer (East Uralian Megazone, South Urals), which occurs on ultramafc rocks, are studied. The trace element composition of chloritolites is characterized by elevated contents of Mn, Ti, V (hundreds of ppm), Cu, zn, Ni, Co, Cr, zr, Li, Sc (tens of ppm), w, zr, Y and REE. Chloritolites contain up to 3 vol. % of disseminated magnetite, ilmenite and accessory minerals (rutile, xenotime, monazite, zircon, apatite, scheelite, U-bearing thorite) from a mineral assemblage, which cocrystallize with the main volume of chlorite. The mineralogical and geochemical features of the Mokhovoe boloto chloritolites and gold-bearing chloritolites of the Karabash massif in the Main Uralian Fault zone are slightly similar. The elevated Ti and P contents of the studied chloritolites, the level of REE contents corresponding to mafc rocks, and the lack of relict chromite indicate their possible metasomatic formation after dolerite dikes known within Chebarkul-Kazbai ultramafc complex. Figures 8. Tables 7. References 14.

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ZIRCON IN HIGH‐MG DIORITE OF THE CHELYABINSK MASSIF (SOUTH URALS): MORPHOLOGY, GEOCHEMICAL SIGNATURE, AND PETROGENESIS IMPLICATIONS

Geodynamics & Tectonophysics ◽

10.5800/gt-2019-10-2-0415 ◽

2019 ◽

Vol 10 (2) ◽

pp. 289-308 ◽

Cited By ~ 1

Author(s):

T. A. Osipova ◽

G. A. Kallistov ◽

M. V. Zaitseva

Keyword(s):

Trace Element ◽

Inductively Coupled Plasma ◽

Isotope Composition ◽

Trace Element Composition ◽

Element Composition ◽

South Urals ◽

Intermediate Composition ◽

Inductively Coupled ◽

Granitoid Massif ◽

Mg Melt

The article is focused on the morphology, trace element composition, U‐Pb and Lu‐Hf systems in zircon in high‐Mg diorite of the Chelyabinsk granitoid massif. Our analytical studies of the U‐Pb and Lu‐Hf isotope systems and the trace element composition were performed using mass spectrometry (MS) with inductively coupled plasma (ICP) and laser ablation (LA) of samples. It is established that the zircon formed at the last stages of crystallization of the basic melt under subsolidus conditions at low (600–700 °C) temperatures, which distinguishes it from the zircon of most other high‐Mg rocks of the intermediate composition. The internal structure of the zircon and the concentration of trace elements are locally altered under the influence of a fluid, which led to a partial disruption of the U‐Pb and Lu‐Hf isotopic systems. For the least altered areas in the zircon crystals, the age of crystallization of the parent high‐Mg melt is 362±2 Ma, which coincides with the age estimated from the geological data. Considering the isotope composition of Hf in the zircon and the trace element concentrations, there are grounds to relate the formation of high‐Mg diorite in the Chelyabinsk granitoid massif with a mixed mantle‐crustal source.

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