Geochemical signs of magmatic commingling in the Dashkesan gabbro-granite intrusion (Dashkesan iron ore deposit, Azerbaijan)

Background. Geochemical signs of magmatic commingling are considered on the example of the Dashkesan Fe–Co deposit using geochemical data and mathematical modeling.

Aim. To develop a petrological-geochemical model of magmatic commingling in the Dashkesan ore deposit.

Materials and methods. The research methodology is based on field data, geochemical data (ICPMS, XRF) analysis of retrospective data and petrographic studies of thin sections.

Results. The influence of the processes of contamination and magmatic commingling is shown using the Dashkesan deposit as an example. This site is associated with the formation of Fe-Co skarn deposits. The rich composition of accessory minerals, variations in textures and structures from hypidiomorphic granular to taxitic, the presence of numerous schlieren and cumulus accumulations of mafic minerals, and numerous xenoliths and enclaves — all are indicative of magmatic commingling processes. The rocks of the first gabbroid phase with increased contents of lithophile and REE elements are characterized by geochemical anomalies; at the same time, lower contents are observed for rocks of further stages of granitoids. The geochemical parameters indicate a relatively enriched magmatic source for the formation of rocks with contamination of the continental crust and subduction-fluid enrichment. These processes led to a deviation in the chemical composition of the Dashkesan rocks from the composition of typical island-arc igneous rocks. The source for the rocks of the gabbro-granite complex was the relatively enriched rocks of the mantle wedge. In addition to the process of melt mixing, the formation of the gabbro-granite complex was accompanied by crustal contamination and subduction enrichment.

1. Abdullaev R.N., Mustafaev G.V., Mustafaev M.A., et al. Mesozoic igneous formations of the Lesser Caucasus and associated endogenous mineralization / ed. E.Sh. Shikhalibeyli. Baku: Elm, 1988. 160 p.

2. Ismail-zade A.D. Petrological interpretation of the process of hybridism in Mesozoic granitoid intrusions of the Lesser Caucasus // ANAS Transactions, Earth Sciences. 2006. No. 2. P. 9—19.

3. Kashkai M.A. Petrology and metallogeny of Dashkesan and other iron ore deposits of Azerbaijan. Moscow, 1965. 888 p.

4. Marfunin A.S. Materials for the petrography of the Dashkesan massif and its contact field // Proceedings of the Geological Institute of USSR. Vol. 165. Petrography section 1955. No. 147. P. 113—142.

5. Mustafaev G.V. Mesozoic granitoids of Azerbaijan and features of their metallogeny. Baku: Elm, 1977. 234 p.

6. Mustafaev G.V. On the hybridism of magmas of the Mesozoic intrusions of the Lesser Caucasus and the femic profile of endogenous mineralization // Magmatism, formations of crystalline rocks and the depths of the earth. Moscow: Nauka, 1974. P. 25—27.

7. Nagiev V.N. Ore deposits of the Azerbaijan Republic: monograph / scientific. ed. S.A. Bektashi; ed. Yu.D. Zamanov. Baku: Elm, 2007. 596 p.

8. Petrographic Code of Russia. Igneous, metamorphic, metasomatic, impact formations. St. Petersburg: VSEGEI Publishing House, 2009. 200 p.

9. Sadikhov E.A. Geochemistry, U-Pb dating and geodynamic conditions for the formation of the gabbrogranite complex of the Lok-Garabakh tectonomagmatic zone (Dashkesan intrusion) // Materials of the conference “Granites and the evolution of the Earth: mantle and crust in granite formation”. Ekaterinburg, 2017. P. 264—266.

10. Sadikhov E.A. Mesozoic plutonic complexes of the Lok-Garabag zone of the Lesser Caucasus: geochemical characteristics, age and magmatic sources. PhD thesis, 2019. P.189

11. Shipulin F.K. Intrusions and ore formation (using the example of Dashkesan). Leningrad: Nauka, 1968. 216 p.

12. Baxter S., Feely M. Magma mixing and mingling textures in granitoids: examples from the Galway Granite, Connemara, Ireland // Mineralogy and Petrology. 2002. Vol. 76. No. 1. P. 63—74.

13. Enclaves and granite petrology / J. Didier & B. Barbarin. Elsevier, 1991. 601 p.

14. Fourcade S., Allegre C.J. Trace elements behavior in granite genesis: a case study. The calc-alkaline plutonic association from the Querigut complex (Pyrénées, France) // Contrib. Mineral. Petrol. 1981. Vol. 76. No. 2. P. 177—195

15. Frost T.P, Mahood G.A. Field, chemical and physical constraints on mafic-felsic magma interaction in the Lamarck Granodiorite, Sierra Nevada, California // Geological Society of America Bulletin. 1987. Vol. 99. P. 272—291.

16. Hibbard M.J The magma mixing origin of mantled feldspars // Contrib. Mineral. Petrol. 1981. Vol. 76. P. 158—170.

17. Hibbard M.J. Textural anatomy of twelve magmamixed granitoid systems / J Didier, B. Barbarin (eds.) // Enclaves and granite petrology. Amsterdam: Elsevier, 1991. Vol. 13. P. 431—444.

18. Wilcox R.E. The idea of magma mixing: history of a struggle for acceptance // J. Geol. 1999. Vol. 107. P. 421—432.