International Journal of Earth Sciences

Trájer, Attila J.

doi: 10.1007/s00531-023-02302-9pmid: N/A

The Pannonian Basin is a sediment-filled back-arc basin which was formed during the Late Paleogene–Neogene period. Such sedimentary rocks like bauxites or kaolinites, which are important with regard to industry in the region, are the products of former weathering processes. However, our knowledge about the palaeoenvironmental conditions which led to the formation of these mineral resources has not yet been integrated. For this purpose, the former biomes, climatic classes as well as karstification, weathering and paedogenic processes were investigated over the last 34 mys using the southeastern regions of China and the United States as climatically analogous regions. By the second half of the Oligocene, the conditions of intensive chemical weathering ceased to exist in the Pannonian Basin, which enabled the formation of lateritic bauxites during earlier periods. However, up to the mid-Serravallian Stage, intensive karstification as well as the formation of haematite-rich ultisols and alfisols continued when humid subtropical climatic conditions came about. The modelled biomes indicate that aridification during the Early to Middle Miocene led to the formation of less dense vegetation, exacerbating the re-deposition of weathering products. These conditions resulted in the accumulation of haematitic and kaolinitic sedimentary rocks in the fossilized karst depressions. The progressive cooling following the mid-Pliocene decreased the intensity of karstification, moreover, the cessation of humid subtropical conditions brought the sedimentation of haematitic and kaolinitic sedimentary rocks in the Pannonian Basin to an end.

Zakrzewski, Adam; Krajewski, Marcin; Kosakowski, Paweł

doi: 10.1007/s00531-023-02311-8pmid: N/A

In this study, we combined the geochemical characteristics based on Rock-Eval pyrolysis and gas chromatography – mass spectrometry (GC–MS) results with the facies analysis. These surveys were conducted within grey to black claystones/mudstones intervals of the Podil’tsi and Kokhanivka formations, related to the Pliensbachian and Toarcian–Bathonian ages, respectively. The geochemical results revealed that the Podil’tsi Formation contains mixed marine/terrigenous, early-mature to mature organic matter. The deposition of this formation took place in dysoxic redox conditions of a sulphate-poor marine palaeoenvironment, with oxygen scarcity within the photic zone, as documented by green- and brown-pigmented Chlorobiaceae. Oleanane is present within the samples from the Podil’tsi Formation, which is uncommon within Lower Jurassic sedimentary rocks. The Kokhanivka Formation contains mostly early-mature, terrestrial organic matter, deposited in suboxic conditions of a sulphate-poor, fluvial–deltaic palaeoenvironment. The absence of aliphatic diterpenoids within the Middle Jurassic strata points to the low significance of conifers in the sediment supply area at this time. All of the Podil’tsi and most of the Kokhanivka formations are characterised by poor hydrocarbon potential. Only the middle part of the Kokhanivka Formation, built by brown, organic-rich claystones, shows fair-to-good hydrocarbon potential. Based on our results, a chemostratigraphic correlation of the Toarcian–Bathonian strata from the Carpathian Foredeep with the same strata from the neighbouring Polish Basin was performed. The juxtaposition of the geochemical and facies results suggests that the interval of brown organic-rich claystones, from the middle part of the Kokhanivka Formation can be related to the Middle–Upper Aalenian Age.

González-Guzmán, Reneé; Velasco-Tapia, Fernando; Weber, Bodo; Schaaf, Peter; Sosa-Valdés, Rogelio; Solari, Luigi

doi: 10.1007/s00531-023-02312-7pmid: N/A

During the Mexican fold-and-thrust belt tectonics, the inboard migration of long-term cordilleran magmatism typifies the geological setting during the Cretaceous–Paleogene period. The Concepción del Oro Igneous Complex (COIC) represents one of the most internal and isolated magmatic pulses that occurred during this magmatic activity. In this work, plutonic rocks from the COIC were studied using petrography, U–Pb geochronology, whole rock and zircon geochemistry, and Rb–Sr and Sm–Nd isotopes. Petrographic observations reveal mainly fine-to-coarse-grained granodioritic composition for most plutonic masses. U–Pb zircon analyzes of four samples from the largest plutonic center of the COIC yielded ages ranging from 42.6 ± 0.2 Ma to 41.8 ± 0.1 Ma. The granodiorites exhibit geochemical features typical of I-type, high-K calc-alkaline, Magnesian rocks. The chondrite-normalized REE diagram summarizes enrichment of LREE ([La/Yb]N = 5.94–19.19) and moderate to slightly negative Eu anomalies (Eu/Eu* = 0.63–0.94). In addition, the mantle-normalized spider diagram shows enrichment of LILE, such as Rb and Ba, and depletion of HFSE, such as Nb, Ta, Ti, and P. Whole-rock and zircon geochemistry indicate a post-collisional setting with an inherited magmatic arc fingerprint. Ti-in-zircon temperatures and zircon saturation thermometry suggest a magmatic origin from evolved and relatively cold melts (~ 700 °C). Moreover, the systematic variations in the ratios of highly incompatible elements, such as La/Sm (6.54–3.79) and Rb/Sr (0.32–0.10), and relatively narrow ranges in Zr/Hf (36.25–48.84) and 147Sm/144Nd (0.0941–0.1261), suggest fractional crystallization as the main petrogenetic process involved in the formation of the COIC rocks. Whole-rock isotopic data suggest a magma source mixing juvenile material with older continental crust, as indicated by 87Sr/86Sr(t = 40) ratios between 0.704583 and 0.707783, 143Nd/144Nd(t = 40) ratios varying in the ranges of 0.512478–0.512702 (εNd(t = 40) = from + 2.18 to − 2.10), and TDM(Nd) ranging from 1.03 to 0.62 Ga. We conclude that the parental source of the COIC was derived from partial melting of the lower crust triggered by emplacement of an underplated magma at the base of the crust during the end of an orogenic cycle.

Maro, Guadalupe; Suzaño, Néstor Omar; Ulberich, Juan Pablo Villalba; Caffe, Pablo Jorge; Viramonte, José María; Viramonte, José Germán

doi: 10.1007/s00531-023-02306-5pmid: N/A

The Huachichocana Subvolcanic Complex (HSC) is one of the easternmost Miocene magmatic complexes from the Central Andes back-arc region. This complex comprises three major sheet-like igneous bodies and contiguous minor intrusions of andesitic to dacitic rocks distinguished by their adakite-like high Sr and Sr/Y values. Based on new detailed data of this system, we explore the genesis of intermediate magmas in the far back-arc region of the Central Andes and complement work on similar rocks from the Eastern Cordillera. We add petrography and mineral chemistry studies and we report new whole rock geochemical and Sr–Nd isotopic data, and a U–Pb zircon age for the HSC. The results suggest that these intrusive rocks were derived from melting of a hydrated mantle source and that the adakite-like composition was acquired through amphibole-dominated fractionation at deep to moderate crustal pressures and by the suppression of early plagioclase crystallization in precursor magmas. The presence of mafic microgranular enclaves is frequent and, along with variations in the composition of phenocrysts and common disequilibrium textures, suggests a significant role of mixing between mafic and intermediate magmas during their ascent and storage in the crust. U–Pb radiometric dating yielded a concordia age of 8.343 ± 0.042 Ma for the andesites of the HSC, coinciding with the period of maximum shortening of the eastern border of the Puna plateau. Nevertheless, this igneous complex is located at the southern margin of the Lípez fault system, a zone of lithospheric weakness that should favor magma emplacement so far east of the trench.

Koglin, Nikola; Meinhold, Guido

doi: 10.1007/s00531-023-02315-4pmid: N/A

In the southeastern part of Chios Island, Greece, exotic blocks of amphibolites and serpentinized peridotite can be found within a narrow, approximately N–S elongated area adjacent to non-metamorphosed sedimentary strata of Triassic age to its west and of Cenozoic age to its east. In this work, we present for the first time petrological and mineral chemical data for the amphibolites and ultramafic rock fragments from SE Chios Island, describe their possible origin and estimate the metamorphic pressure–temperature conditions and the age of metamorphic overprint. The protoliths of the amphibolites were mafic rocks of enriched (Type I amphibolite) and normal (Type II amphibolite) mid-ocean ridge character metamorphosed under upper amphibolite-facies conditions at 640–780 °C and 5–7 kbar. U–Pb isotopic data from titanite from three amphibolites yielded early Middle to early Late Jurassic lower intercept ages, which we interpret as the age of metamorphism during oceanic lithosphere emplacement. The peridotite is strongly serpentinized, mainly containing lizardite, which implies low-grade metamorphic conditions. With the exception of alteration rims, Cr- and Mg-numbers of the chrome spinel from the serpentinized peridotite range from 10–26 and 69–79, respectively, a range similar to abyssal peridotites of the subcontinental lithospheric mantle. We suggest that the amphibolites and ultramafic rocks represent separate fragments within a mélange, most likely of tectonic rather than accretionary origin. Metamorphism of the amphibolites took place prior to their presumed emplacement in the mélange. The mafic and ultramafic rock fragments of Chios preserve a different sort of subcontinental signature than that largely reported elsewhere within the Eastern Mediterranean ophiolite belts. A correlation with rocks of mélange units in western Turkey or in the northern and/or southern Aegean region is discussed.

Dung, Pham Thi; Usuki, Tadashi; Tran, Hoa Trong; Hoang, Nguyen; Usuki, Masako; Minh, Pham; Nong, Anh Thi Quynh; Nguyen, Y. Viet; Hieu, Pham Trung

doi: 10.1007/s00531-023-02307-4pmid:

Helmy, Hassan M.; Tütken, Thomas; Lotfy, Hamza

doi: 10.1007/s00531-023-02304-7pmid: N/A

Gómez-Peral, Lucía E.; Arrouy, M. Julia; Raigemborn, M. Sol; Ferreyra, Camila; Penzo, Victoria; Sial, Alcides N.; Poiré, Daniel G.

doi: 10.1007/s00531-023-02308-3pmid: N/A

The sedimentary infill of the Tandilia Basin is characterised by at least four different stages of deposition during the Neoproterozoic (< 1160 to ~ 550 Ma), two of them recognisable in the Sierras Bayas Group and two in the La Providencia Group. The Villa Mónica Formation, representing the first stage of basin infill (< 1160 to < 720 Ma), consists of a lower siliciclastic section that passes transitionally into an upper dolostone section. This dolostone platform, rich in standard Cryogenian stromatolites, was interpreted as deposited under typical cold, suboxic to oxic seawater conditions. A detailed analysis of the dolostone section allowed us to distinguish two karst events imprinted in the formation. The hypogene karst genesis is interpreted as hydrothermal with the development of Mn-oxide dykes associated with intense silicification and brecciation of the host dolostones. The younger epigene karst, which developed over the post uplifted unit, is related to intense weathering and subaerial exposure with the generation of an irregular surface in its upper contact. This unconformity, known as the Piedra Amarilla Surface, is represented regionally in the Tandilia System. It may have implied a post-uplift period of erosion, dissolution and non-deposition that predates the accumulation of the ~ 400-m-thick overlying succession (the Sierras Bayas and La Providencia groups). Accordingly, the Piedra Amarilla Surface may represent a large spatio-temporal interval bounding two contrasting histories in the basin infill, which would justify separating the Villa Mónica Formation from the Sierras Bayas Group. This karst-related surface may be considered a fingerprint of the transition from the break-up of Rodinia to the configuration of southwestern Gondwana.

Iqbal, Shahid; Bibi, Mehwish; Wagreich, Michael

doi: 10.1007/s00531-023-02310-9pmid: N/A

Bauxite deposits are residuals of intense lateritic weathering under warm and humid palaeoclimates. The Triassic–Jurassic Boundary (TJB) interval in the Salt Range, Pakistan, provides one such case of bauxite deposits formation along the SW tropical Neo-Tethyan passive margin. Thick, red bauxites/bauxitic clays occur at the contact of the Upper Triassic Kingriali Formation and the Lower Jurassic Datta Formation. These bauxites are rich in kaolinite, haematite, boehmite (Al2O3 and Fe2O3), and are depleted in silica (SiO2). Geochemical proxies of the succession signal intense chemical weathering of the parent siliciclastics under Mesozoic “greenhouse” conditions. Certain trace elements and Rare Earth Elements (REEs) are enriched up to seven times compared to mean Upper Continental Crust (UCC) values. These bauxites are synchronous with the Amir-Abad bauxites of the Alborz Mountains, central Iranian Plateau, that occur between the thick Triassic dolomite/dolomitic limestones of the Elika Formation and the Lower Jurassic Shemshak Formation. Thus, the Salt Range, Pakistan, provides evidence for the eastward extension of the Irano-Himalayan bauxites that are extended westward into Mediterranean bauxites, and the western Tethys by correlation with European bauxites. The TJB bauxites in the Salt Range support increased chemical weathering on the SW Neo-Tethyan passive margin and correspond to an associated sea-level fall during this time interval. This supports the Neo-Tethyan tectonics contribution in the formation of bauxite deposits during the Triassic–Jurassic in addition to the widely studied karst-bauxites that formed in response to the subduction and orogenic processes in the Paleo-Tethys.

Ghorbani, Mohammad Reza; Paydari, Mohammad; Ahmadi, Parham; von Quadt, Albrecht; Ahadnejad, Vahid; M. Cottle, John; Graham, Ian T.; Ahmadian, Jamshid; Ahmadvand, Ahmad

doi: 10.1007/s00531-023-02313-6pmid: N/A

Vast and geochemically diverse volcanic rocks from the western Alborz Magmatic Assemblage (AMA) represent the back-arc of the central Iran Neotethyan arc (Urumieh–Dokhtar Magmatic Assemblage; UDMA). Volcanic rocks of the west AMA record valuable information on the timing, source region(s) and geodynamic setting of magmatism. Over 30 days of field study and sampling, investigation of 170 thin sections, 30 whole-rock geochemical analyses, 13 whole-rock Sr–Nd isotopic ratios and U–Pb age dating of zircon separates from 7 samples furnished the present study data. Eocene (38.5 Ma) OIB-type volcanic rocks from South Kaleybar indicate an anorogenic (extensional) setting. This lithospheric-scale extensional event induced influx of asthenospheric mantle into the sub-arc wedge, of which the partial melts differentiated to produce OIB-type melts. The OIB-type melts incorporated some inherited zircons in their ascent through  the Cadomian crust. A continued extensional regime led to asthenospheric upwelling and produced mafic melts that produced 27.5-Ma-old subalkaline series volcanics. The LILE-depleted signature of the South Kaleybar subalkaline volcanic rocks implies that their mantle source region experienced previous partial melting event(s), probably during OIB-type magmatism in the Eocene. Alkaline volcanism (24.4 Ma) and concurrent high-silica adakitic volcanism (24.3 Ma–23.4 Ma) followed subalkaline magmatism. The alkaline rock signature in the study area range from ‘Nb–Ta depleted’ to ‘plume-type’. This is consistent with lithosphere–asthenosphere interaction in an arc-related setting. Simultaneous partial melts of delaminated lower crustal rocks reacted with the asthenosphere and produced adakitic melts. Asthenospheric, lithospheric and crustal contribution to the magmatism in South Kaleybar express the back-arc signature of magmatism in Eocene to Late Oligocene times.