Gücer, Mehmet Ali; Çimen, Okay; Aktağ, Alican; Keskin, Serdar

The growing demand for critical minerals driven by the global energy transition and advanced technologies highlights the importance of unconventional metal reservoirs. This study investigates the Ni-, Co-, V-, and Pt-enriched Dilli manganese deposit (Kemaliye-Erzincan, Eastern Türkiye) to constrain the mineralogical, geochemical, and genetic controls on critical metal enrichment in Mn oxide mineralization. An integrated approach combining field observations, petrography, X-ray diffraction (XRD), whole-rock geochemistry, mineral chemistry, and stable C-O isotope analysis was applied to better understand the potential origin of critical mineral enrichments. The mineralization is dominated by Mn4+-bearing oxides, principally pyrolusite and hollandite, accompanied by minor rhodochrosite. High MnO (39-64 wt%) and very low Al2O3 and Fe2O3 contents indicate chemical precipitation with negligible detrital input. Discrimination diagrams and trace-element systematics consistently support a structurally controlled hydrothermal origin. Chondrite-normalized REE patterns display low total REE and very low Nd contents comparable to typical hydrothermal deposits, whereas neutral to slightly positive Ce anomalies and non-chondritic Y/Ho ratios suggest limited oxidative interaction with surface-derived fluids rather than primary marine hydrogenetic growth. Stable C–O isotope compositions of co-genetic calcite are inconsistent with a purely marine depositional environment and indicate precipitation from low-to moderate-temperature hydrothermal fluids. Mineral chemistry reveals strong phase-specific partitioning: hollandite preferentially incorporates V and Ba, whereas pyrolusite is enriched in Ni. Cobalt occurs in both phases, whereas Pt may also be present in both Mn oxide phases, suggesting that trace-element distribution is influenced by both crystallochemical and physicochemical controls. The enrichment of Ni, Co, and Pt is most plausibly linked to hydrothermal fluid circulation through ultramafic units, which likely acted as the primary metal source prior to precipitation. The Dilli deposit thus represents a structurally controlled hydrothermal Mn system enriched in critical metals, emphasizing the exploration relevance of Mn oxide mineral chemistry in identifying alternative sources of critical metals in Türkiye.

İncele

Sayit, Kaan; Çevik, Özlem; Aktağ, Alican; Erdoğu, Burçin; Bamyacı, Onur; Vuruşkan, Osman; Sivil, Coşkun

The jades from Ulucak Höyük (İzmir, Turkey) are green-colored in hand specimen, and combined petrographic, XRD, and whole-rock analyses indicate that they mainly comprise jadeitic clinopyroxene, characterizing them as jadeite-bearing jades. Primitive mantle (PM)-normalized multi-element patterns reveal two distinct chemical groups. Both groups display depletion in Th and U; however, Group 1 shows a narrower elemental range and marked positive Pb anomaly. The second group, on the other hand, displays a wide elemental range in most elements and strong negative anomalies in Zr and Hf ([Nd/Zr]PM = 1.6–4.2; [Sm/Hf]PM = 1.8–3.5). Regarding REE systematics, both groups are characterized by weak positive slopes ([La/Yb]Ch = 1.7–5.3). However, whereas Group 1 shows coherent LREE-enriched trends, Group 2 displays flat- to LREE-enriched patterns with a wide range in Eu. When the geochemical features of Ulucak jades are compared with the high-pressure (HP) metamorphic rocks from Turkey and Greece, the similar multi-element patterns of Syros eclogites (Greece) to Group 2 Ulucak jades make Syros a possible source area for the Ulucak artefacts. On the other hand, the geochemical resemblance of the Sifnos jadeite-bearing gneisses to Group 1 Ulucak jades may raise the possibility of this island being another source for the Ulucak jades.

İncele

Aktağ, Alican; Sayit, Kaan; Furman, Tanya; Peters, Bradley J.

The Sr-Nd-Hf-Pb isotope geochemistry of the Late Miocene Tunceli Volcanics suggests that they are the products of mixed asthenospheric and lithospheric mantle melts. The combined elemental and mineral chemistry data additionally indicate that a pyroxenite component of lithospheric origin is involved in their genesis. Calculations favor melting depths of ∼2 GPa for the Tunceli lavas, that is, deeper than the current lithosphere-asthenosphere boundary beneath Eastern Anatolia. Geochemical data suggest that during regional Neo-Tethyan subduction, dense (i.e., pyroxenite-bearing) domains formed by progressive melt intrusion into the lower lithosphere resulted in gravitational instabilities. This unstable density configuration eventually led to the foundering of the eastern Anatolian lithosphere in the Late Miocene, resulting in progressive melting of fusible pyroxenite-bearing domains at asthenospheric depths. We demonstrate that these pyroxenitic melts mixed with ambient asthenospheric melts and generated the Tunceli lavas.

AtıfScopus7·OpenAlex9

İncele

Aktağ, Alican; Sayit, Kaan; Peters, Bradley J.; Furman, Tanya; Rickli, Jörg

Quaternary Elazığ mafic alkaline volcanism is part of the anorogenic volcanic system of the circum-Mediterranean region, and it provides crucial insights into the chemical nature of the mantle source domains beneath eastern Turkey. Elemental and isotope geochemistry reveals that these mafic lithologies are mainly free of crustal contamination, reflecting geochemical signatures inherited from partial melting of their mantle sources. The trace element and Sr-Nd-Hf-Pb isotope systematics of the most primitive members of this volcanism are consistent with a predominant contribution from a sub-lithospheric component which compositionally resembles component C, believed to be common to global OIBs and MORBs. However, the total range of the isotope data also requires the involvement of two additional mantle components into their genesis: a depleted asthenospheric component (DM) and an enriched component (EM-type) representing metasomatized lithospheric mantle. We propose that the recycled oceanic lithologies with C-like signatures are dispersed in the asthenospheric mantle beneath eastern Anatolia and have undergone mixing with the depleted mantle matrix. When considering these with the melting models, it appears that the garnet-facies partial melts of the C-DM mixture have experienced a small degree of interaction with the melts from an SCLM domain modified by slab-derived melts and/or fluids. The metasomatized SCLM domain may be intrinsic to the eastern Anatolian lithosphere or occur as pods embedded in the asthenosphere. The chemical characteristics of the Elazığ Volcanics may confirm the wide-range dispersal of the common component in the sub-lithospheric mantle beneath the region extending from western Europe to eastern Turkey. However, the common component resides beneath Anatolia appear to have distinct composition (i.e., Pb isotope systematics) than the ubiquitous component shared mostly by European intraplate volcanics (i.e., LVC/EAR).

AtıfScopus3·OpenAlex4

İncele

Aktağ, Alican; Önal, Ayten Öztüfekçi; Sayit, Kaan

The East Anatolian Accretionary Complex (EAAC) comprises an ideal example of post-collisional volcanism within the Africa-Eurasia collision zone. The Miocene mafic Tunceli Volcanics, as a part of this post-collisional volcanic system, are located in the western termination of EAAC. The mafic Tunceli Volcanics are characterized by mildly alkaline and tholeiitic basalts, in which olivine, clinopyroxene and plagioclase characterize the main mineralogy. The role of fractional crystallization (FC) and assimilation combined with fractional crystallization (AFC) processes appear to be negligible in the petrogenesis of the primitive mafic Tunceli Volcanics. Relative enrichment in large ion lithophile elements (LILE), Th and La over high field strength elements (HFSE) and heavy rare earth elements (HREE) suggest contribution from a metasomatized mantle source. The wide range of ratios displayed by these elements also calls for some asthenospheric input for the genesis of these volcanics. The metasomatizing agents can be attributed to a past subduction event, probably during the closure of Neotethys. Considering also the geophysical constraints, which limits the lithospheric thickness to about 70–75 km around the region, a melt mixing between lithospheric and asthenospheric melts generated at different depths appear to be an important process in the petrogenesis of these lavas. The combined geochemical and geophysical data, therefore, necessitate a geodynamic model with some remnant lithospheric mantle underlying the Eastern Anatolian region.

AtıfScopus10·WoS11·OpenAlex13

İncele