GEOCHEMICAL FEATURES OF THE KYPLATAP AG-AU ORE OCCURRENCE IN CENTRAL CHUKOTKA

The article considers the geochemical features of unconventional mineralization in secondary quartzite’s of the Kyplatap ore occurrence, located on the southeastern flank of the volcanic dome structure (VDS) of the same name, complicating the Palyavaam-Pykarvaam volcanotectonic depression (VTD) in the Chaun zone of the Central Chukotka sector of the Okhotsk-Chukotka volcanic Belt (OChVB). The Kyplatap VDS was formed due to the intrusion into the Late Cretaceous Alkaquun volcanites of a large laccolith-like subvolcanic body composed of rhyolite-trachyriolite-trachydacites. Based on the geochemical studies of the Kyplatap ore occurrence, the authors compiled a representative database of geochemical data, including the results of analyses of express-RFA, PKSA and XSA with coordinates and composition of ores and rocks. Correlation analysis of the database showed a positive relationship between Au and Ag, as well as Sb for ore mineralization, and a negative correlation of these elements with the association of the rock group of elements (Ti, Y, Zr, Nb and Yb) that were removed during ore formation. The authors also distinguished the second rock group of elements (K, Ga, Sn, Ba, V, W, Pb, Sc, La and B), characterized by medium and weak correlation of the first group of elements. They calculated the coefficients of enrichment and deficiency of ore-forming elements for the samples taken within the ore zones of the Kyplatap ore occurrence. The extreme enrichment group includes elements Au, Ag, Sb, Bi, As, the average contents of which are 100 times or more, and the minimum concentrations are at least 2-10 times higher than the average contents in the upper crust. The normal enrichment group includes elements S, Sn, Cu, Zn, Mn, Mo and Pb, the average contents of which are 2-10 times, and the maximum concentrations are 5-100 times higher than the average concentrations of the upper crust. The obtained values of the enrichment coefficients indicate a sufficiently intensive metensomatoses and ore formation within the Kyplatap ore occurrence. The Kyplatap ore occurrence is located in the epicenter of a concentric-zonal mineral-forming system. In the nuclear zone, chemical elements Ag, As, Sb, Cu, Pb, Mo are brought in and Sn, V, Co, Ni, Sc and Cr are removed to the periphery, while Au is localized both in the nuclear zone, forming Ag-Au mineralization here, and in the peripheral part, forming satellite dike occurrences of the Au-rare-metal type. The results of factor analysis correspond to the data of correlation and enrichment coefficients. The level of erosion section of the Kyplatap ore occurrence, according to factor analysis, is estimated as moderate. The presence of a large isometric silver anomaly, suggests the possibility of large-volume mineralization development within the limits of the Kyplatap ore occurrence.

1. Bely V. F. Geology of the Okhotsk-Chukchi volcanic belt. Magadan, SVKNII FEB RAS, 1994, 76 p. (In Russian).
2. Sokolov S. D., Bondarenko G. E., Morozov O. L., Grigoriev V. N. The transition zone of the Asian continent — Northwestern Pacifica in the Late Jurassic-Early Cretaceous. Theoretical and regional problems of geodynamics. Moscow, Nauka, 1999, pp. 30—82. (In Russian).
3. Tikhomirov P. L., Prokofiev V. Yu., Kalko I. A. Kalko A. V., Nikolaev Yu. N., Kobayashi K., Nakamura E. Post-collisional magmatism of Western Chukotka and Early Cretaceous tectonic restructuring of Northeast Asia. Geotectonics, 2017, no. 2, pp. 32—54. (In Russian).
4. Petrov S. F. Material composition, textural and structural features and issues of typification of gold-silver mineralization of the Kyplatap volcanoplutonic structure (Central Chukotka). Mineralogy and genetic features of gold and silver deposits. Magadan, SVKNII FEB RAS, 1996, pp. 105—119. (In Russian).
5. Volkov A. V., Sidorov A. A. Predictive prospecting model of gold deposits associated with granitoid intrusions in the Arctic zone of Russia. Arktika: ekologiya i ekonomika. [Arctic: Ecology and Economy], 2018, no. 3 (31), pp. 84—99. DOI: 10.25283/2223-4594-2018-3-84-99. (In Russian).
6. Taylor S. R., McLennan S. M. The continental crust, its composition and evolution. Moscow, Mir, 1988, 384 p. (In Russian).
7. Kalko I. A. Geochemical parameters and characteristics of the gold-silver fields of the outer zone of the OCHVP and criteria for detecting industrial mineralization in them. Dissertation for the degree of Candidate of Geological and Mineralogical Sciences. Moscow, MSU, 2009, 197 p. (In Russian).
8. White N. C., Hedenquist J. W. Epithermal gold deposits: Styles, characteristics and exploration. SEG Newsletter, 1995, vol. 23, pp. 1, 9—13.
9. Hedenquist J. W., Arribas A., Gonzalez-Urien E. Exploration for epithermal gold deposits. SEG Rev., 2000, vol. 13, pp. 245—277.
10. Volkov A. V., Sidorov A. A., Savva N. E., Kolova E. E., Chizhova I. A., Murashov K. Yu. Geochemical features of volcanogenic ore formation in the northwestern segment of the Pacific ore belt. Volcanology and seismology, 2017, no. 6, pp. 3—20. (In Russian).
11. Savva N. E., Bryzgalov I. A., Tyukova E. E. Tin-porphyry formation of the Prikaramkenya (geological-structural and mineralogical features). Bull. of the North-East Scientific Center of FEB RAS, 2009, no. 4, pp. 2—14. (In Russian).
12. Lugov S. F., Makeev B. V., Potapova T. M. Regularities of formation and placement of tin ore deposits of the North-East of the USSR. Moscow, Nedra, 1972, 360 p. (In Russian).
13. Volkov A. V., Savva N. E., Sidorov A. A., Chizhova I. A., Kolova E. E., Alekseev V. Yu. Epithermal gold-silver deposit Agan and prospects for the detection of highly sulfidized type mineralization in the North-East of Russia. Geology of the ore deposits, 2015, vol. 57, no. 1, pp. 25—47. (In Russian).