International Geology Review

Satpathi, Kausik; Yi, Keewook; Nasipuri, Pritam

doi: 10.1080/00206814.2025.2499899pmid: N/A

This article presents the findings of a petro-chronological investigation on two-pyroxene mafic rocks (orthopyroxene – clinopyroxene > plagioclase > quartz > biotite) found as enclaves within 2500 Ma aged magmatic charnockites in the East Dharwar Craton (EDC). The Mg number (100MgO/(MgO+FeO)) of the analysed samples range between 42 and 57. The orthopyroxene-clinopyroxene and orthopyroxene-biotite associations are stabilized at around 1000–1050°C, 0.7–0.8 GPa and 650°C, 0.6–0.7 GPa, respectively. Chemically zoned monazites within pyroxene and plagioclase exhibit U-Th-Pb total age clusters that span 2638 Ma in the core, 2539 Ma in the rim surrounding the core, and 2458 Ma in the outermost part of the monazite grains. The zircon grains yield an upper intercept age of 2506 ± 13 Ma. The geochemical results, pressure- temperature and geochronological data suggest the existence of Nb-rich, Ti-depleted mafic rocks in the EDC proto crust at ~ 2600 Ma, causing Neoarchean UHT metamorphism. Monazite formation at 2536 Ma was associated with the intrusion of charnockites in the EDC, resulting from the amalgamation of several crustal blocks. The < 2500 Ma monazite forms during isothermal cooling. The oldest (2638 Ma) tectonic episodes overlap with the timing of crustal growth and stabilization of the Kenorland supercontinent.

Lv, Dawei; Cao, Kai; Zhang, Zhihui; Raji, Munira; Song, Cuiyu; Wang, Luojing; Ma, Chao; Wu, Dun; Lv, Weikui

doi: 10.1080/00206814.2025.2503899pmid: N/A

The Late Palaeozoic period is known for containing coal-bearing strata on both land and in the sea, and for its potential influence on sea levels due to glaciation, particularly in North China. However, our understanding of the processes behind coal accumulation during this time is limited due to lack of a reliable timeframe. In our research, we analysed the cyclical patterns in the Late Palaeozoic Taiyuan Formation using data from natural gamma-ray (GR) measurements from two boreholes (ZJC33 and XJC04) in the Huainan Coalfield in southern North China. Our analysis revealed distinct cycles in the Taiyuan Formation, with lengths of approximately 8.6 m, 2.5–1.7 m, and 1.1–1.0 m, which we identified as related to long eccentricity, short eccentricity, and obliquity based on correlation coefficient (COCO) analysis. We have constructed a floating ~5.3 Myr for the Taiyuan Formation. We have established an absolute astronomical time scale of 301.13 Ma to 295.83 Ma for the Taiyuan Formation. This was done using the volcanic ash age of 301.13 million years (with an error margin of ± 0.20 million years) at the bottom of the Taiyuan Formation as a reference point. The results indicate a significant correlation between coal seam development in the Taiyuan Formation and the minimum of the 405-kyr cycle, suggesting that orbitally forced variations in terrestrial clastic input may have been the dominant control on coal accumulation. This study is important for understanding the orbital factors influencing climate evolution and coal sedimentation during the Carboniferous-Permian period.

Tomek, Filip; Černý, Jan; Lutovský, Michal; Pospíšil, Lubomil; Vitouš, Petr; Sokol, Luboš; Danielová, Ema; Hájková, Zuzana

doi: 10.1080/00206814.2025.2503902pmid: N/A

Říp Hill, a volcanic structure near the Eger Rift of the European Cenozoic Rift System, holds deep cultural significance for the Czech nation. According to legend, Forefather Czech (Bohemus) and his Slavic tribe declared the surrounding land their new home around the 6th or 7th century, marking the symbolic beginning of Czech history. Despite its prominence, the geology of Říp Hill remains underexplored. The complete Bouguer anomaly map reveals intersecting NE–SW negative and NW–SE positive lineaments. The NW–SE lineament is interpreted as a dense nephelinite dike parallel to the Elbe tectonovolcanic zone emplaced during N–S horizontal extension, which induced sinistral shearing and segmented the dike into an E–W en-echelon array. These inferred segmented dikes, identified by magnetic anomalies, may have served as volcanic feeders. The nephelinite body above the plumbing system represents a lava lake as shown by columnar joints forming an inverted fan, overlying entablature, and shallow concentric magnetic foliations. We speculate that the eroded crater was of a phreatomagmatic maar-type. Indirect evidence includes the large aerial extent of the nephelinite body, a circular gravity low around the hill, underlying groundwater-saturated Cretaceous sedimentary rocks, and analogies with similar Cenozoic maar-diatreme volcanoes in the Bohemian Massif.

Maharani, Ni Luh Sri

doi: 10.1080/00206814.2025.2501668pmid: N/A

Novilia,

doi: 10.1080/00206814.2025.2501659pmid: N/A