Post-Mineralization, Cogenetic Magmatism at the Sungun Cu-Mo Porphyry Deposit (Northwest Iran): Protracted Melting and Extraction in an Arc System

Abstract

The Sungun porphyry ore deposit is located in Eastern Azarbaijan province, Northwestern Iran. The oldest intrusive pulse in the region is a quartz-monzonite pluton, which hosts the porphyry copper-molybdenum mineralization. The Sungun Copper Mine includes the mineralized Sungun porphyry as well as six groups of cross-cutting and lithologically distinct post-mineralization dykes. The composition of these dykes ranges from quartz diorite, gabbro, diorite, dacite, lamprophyre, and microdiorite. Quartz diorite and dacite dykes are the oldest and youngest dykes, respectively. Based on their cross-cutting relationships, the composition of the dykes tend to become more primitive through time. The dykes strike Northwest–Southeast with Southwest dip, sub-parallel to the reverse faults within the deposit area. The lamprophyric dykes range from phonotephrite, to trachybasalt, tephrite, and basanite. The quartz-monzonite porphyry (SP) and the post-mineralization dykes (DK1-DK3) have clear and distinct negative anomalies of Ti, Zr, P, Pr, Ce, and Nb, as well as positive anomalies of Cs, U, K, Pb, and Nd with respect to primitive mantle. Microdioritic dykes (MDI) show depletion of Ti, Nb, P, Ta, Th, Yb, and Zr, and enrichment of Cs, Ba, U, Pb, Nd. The similarities in trace element abundances and patterns in the porphyry and post-mineralization calc-alkaline dykes implies a single source and fractional crystallization as the main mechanism controlling magmatic evolution in a collisional environment. Lamprophyric dykes have enrichment of LREE and LILE and depletion of HREE and HFSE such as Ti, Nb, and Ta. The parent magma of the lamprophyric dykes (LAM) was likely derived by low degrees of melting of a garnet lherzolite mantle peridotite. The 87Sr/86Sr and 143Nd/144Nd ratios range from 0.704617 to 0.706464 and from 0.512648 to 0.512773 for the dykes suggesting that the parental magmas came from a progressively more enriched mantle. Isotope ratios of 87Sr/86Sr and 143Nd/144Nd support a cogenetic relationship of porphyry and calc-alkaline dykes, except for the microdiorite ones. A common primary melt underwent gravity differentiation in a deep magmatic chamber to form a dioritic magma. This subsequently migrated to shallower levels to evolve further and feed individual dyke groups into the Sungun porphyry.

Mineralogy, mineral chemistry and thermobarometry of post-mineralization dykes of the Sungun Cu–Mo porphyry deposit (Northwest Iran)

“…Dykes may represent residual melts that were reactivated after the mineralizing event and intruded the deposit. The whole-rock geochemical studies [51] support this interpretation. Both rock suites have similarities in their rare earth element patterns as well as strontium and neodymium isotopes, which indicates a common source and evolutionary processes.…”

“…Both rock suites have similarities in their rare earth element patterns as well as strontium and neodymium isotopes, which indicates a common source and evolutionary processes. The Sungun porphyry stock is therefore the oldest and most felsic member of the magmatic complex [51], with later intrusions tapping more primitive and potentially recharged portions of it to form quartz diorite, diorite and gabbrodiorite.…”

Geochemistry and Petrogenesis of Shoshonitic Dyke Swarm in the Northeast of Meshkinshahr, NW Iran

“…This caused localized upwelling in the metasomatized mantle wedge, leading to partial melting that formed the Tertiary magmatism of the Urmia-Dokhtar and Alborz-Azerbaijan zones. Due to subduction, the Neotethys Ocean closing and the post-collision processes, several porphyry copper deposits were formed [120,121]. Eocene to Oligo-Miocene lava and associated plutonic rocks with high-K calc-alkaline or potassic affinities occur only in Armenia and the northwest of Iran [122][123][124].…”

Mineralogy and Mineral Chemistry of Dioritic Dykes, Quartz Diorite Enclaves and Pyroxene of the Sungun Cu-Mo Porphyry Deposit, East Azerbaijan, Iran

“…The global distribution of known Cu-Au porphyry deposits shows a clear spatial relationship with volcanic arc terranes at convergent plate margins (e.g., [1,3]). The Sungun Cu-Mo porphyry deposit, which is the focus of this study, was formed in a post-collisional environment [4]. Studies of the Sungun plutonic rocks and deposit, thus, provide the opportunity to document petrological and geochemical controls that affect mineralization in such environments.…”