DISTRIBUTION OF GOLD IN IGNEOUS GRANITOID COMPLEXES IN THE CENTRAL AND SOUTHWESTERN AREAS OF EASTERN TRANSBAIKALIA
A.M. Spiridonov, V.D. Kozlov, L.D. Zorina, V.I. Men'shikov, and V.A. Bychinskii
V.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, Irkutsk, 664033, Russia
Keywords: Granitoids, granitoid formations, igneous complexes, gold concentrations in granitoids, gold mineralization, cluster analysis of correlations between gold and trace-element concentrations
Pages: 846-856
Abstract
The distribution of gold in rocks from some igneous complexes of the central and southwestern areas of eastern Transbaikalia (Daurian, Aga, and Argun structure-formational zones) was studied by quantitative extraction-atomic-absorption analysis and mass spectrometry with inductively coupled plasma (Element-2 mass spectrometer). High gold concentrations (on average, 0.0043 ppm) are typical of the most widespread hornblende-biotite granodiorites and granites of the main phases of batholith intrusions in the Upper Paleozoic Unda complex in the east of the study area and in the Triassic-Middle Jurassic Kyra complex in the west. The rocks of the Early-Middle Jurassic (Sokhondo) and Middle-Upper Jurassic (Shakhtama, Kharalga, and Kukul'bei) complexes have much lower Au concentrations (mainly 0.0014-0.0030 ppm), with the minimum ones established in the Shakhtama complex. During the magmatic differentiation of granitoid intrusions, the concentrations of gold in the late leucogranite differentiates decreased.
The Au concentrations in the studied complexes do not depend on the composition of the host terrigenous rocks of different ages, which evidences the endogenous nature of the revealed differences in Au concentrations in the regional granitoids. Abnormally high concentrations of gold in some studied samples are observed mainly to the regional hydrothermal mineralization occurrences.
The classification R-type cluster analysis showed that all variables of the studied igneous rocks are subdivided into three groups by the degree of correlation. Gold shows a distinct tendency to the correlation with siderophile oxy- and sulfurophile groups of metals. The Q -type analysis generally confirmed the correctness of the known formational classification of the regional granitoids.
|
