Journal of Asian Earth Sciences: X最新文献

The evaluation of the geothermal potential of the granitic rocks is important in long-term sustainable renewable energy projects due to increasing energy demand. The Eastern Pontides Orogenic Belt in NE Turkey contains a variety of granitic plutons changing in age, size, and composition. In this paper, we discussed the temporal and spatial distribution of radiogenic heat production by using the contents of heat-producing elements (U, Th, K) of the granitic plutons. The average U, Th, and K concentrations for the granitic plutons are 2.97 ± 0.95 ppm, 13.48 ± 3.48 ppm and 2.69 ± 0.47 wt% for Paleozoic plutons, 1.83 ± 0.98 ppm, 8.58 ± 5.10 ppm and 1.77 ± 0.80 wt% for Jurassic plutons, 5.24 ± 1.64 ppm, 26.02 ± 6.43 ppm and 3.17 ± 0.49 wt% for Cretaceous plutons, and 3.82 ± 0.90 ppm, 15.79 ± 4.27 ppm and 2.88 ± 0.40 wt% for Eocene plutons, respectively. Radiogenic heat production rates are 1.43–2.73 µW/m³ for Paleozoic plutons, 0.74–1.70 µW/m³ for Jurassic plutons, 0.66–6.28 µW/m³ for Cretaceous plutons and 1.15–5.22 µW/m³ for Eocene plutons. The studied plutons were classified as low- to moderate heat-producing granitoids. However, some Cretaceous and Eocene granitic plutons with radiogenic heat production values of 5.22–6.28 µW/m³ are considered as high heat-producing granitoids. The thermal indications in the region can be related to radiogenic heat generation and the neotectonic activity of the region. Considering the large volume of the Cretaceous- and Eocene- aged granitic plutons in the Eastern Pontides Orogenic Belt, the moderate to high radiogenic heat production of the granitic plutons in some areas has a significant geothermal impact and can be considered as the potential of enhanced geothermal systems for the future energy demand of the region.

Sedimentation of the Paleogene and Neogene belts in the Indo-Burma Range (IBR) involved a complex tectonic system letting provenance of both the belts poorly constrained. We made an attempt to investigate provenance, tectonic setting, paleoclimate, and depositional environment of the Renji Formation (Paleogene belt) and the Bhuban Formation (Neogene belt) in the Barak basin of western Manipur employing whole-rock geochemistry and petrography. A semi-arid climatic condition has been indicated for the weathering and liberation of sediments in the source terrain. Derivation of first cycle sediments from mafic and felsic rocks with minor contribution from the metamorphic rocks is suggested but the former seems to have dominated the Renji Formation. A shift in the provenance vis-a-vis differential chemical weathering of the mafic-felsic rocks at the source is attributed. Research results also suggest supply from deformed and elevated craton, presumably the Indian craton, during the Himalayan orogeny. Sedimentation of the Renji Formation took place in a sub-oxic deltaic environment in contrast to the Bhuban Formation which developed in an oxic shallow marine mixed tidal flat environment.

The eastern part of the Sakarya Zone, known as the Eastern Pontides, is represented by a south-facing carbonate platform during the Late Jurassic-Early Cretaceous. The shallow marine carbonate sedimentation is masked by hemipelagic sedimentation during the Turonian to Coniacian. The Turonian-Coniacian strata are widely exposed in the Gümüşhane area. In this study, we present new microfacies and geochemical data that can provide new insights into the palaeo-oceanic conditions during the time of their deposition.

These strata consist of yellow to gray, thick-bedded, graded calcarenites, calcilutite, pelagic limestone, and monogenic conglomerates. The dominant components are carbonate fragments, including dolomites and limestone, as well as allochthonous bioclasts. Volcanic rock fragments, quartz, cherts, and glauconites are also present, with their abundance varying along the section. The micritic component and planktonic fauna exhibit an increasing abundance in the upward direction, indicating a gradual deepening of the depositional environment. Hence, the analyzed samples can be interpreted as transgressive series deposited on slopes or the deep shelf basin.

Furthermore, these strata exhibit distinct V/(V+Ni) and Ni/Co ratios without a notable negative Ce anomaly, suggesting relatively oxygen-reduced conditions. They also show a slight enrichment in alkali elements (Rb and Cs) and post-transition elements (Ga), and LREE, indicating intense weathering. The Ga/Rb and K/Al values further support warm and humid Cretaceous conditions. Thus, the Turonian-Coniacian strata offer valuable information about ancient environments, climate conditions, and the basin evolution of the Tethys Ocean in the Eastern Black Sea region.

Currently, the interpretation scheme for strike slip faults in the central Tarim Basin does not typically take into account the depth of tear faults. This paper specifically explores this aspect, focusing on two tear faults (Nos. 4 and 7) to examine the thick-skinned and thin-skinned systems in the area. By utilizing high-resolution seismic data, we discovered that No. 4 Fault is a thick-skinned tear fault whereas No. 7 Fault is a thin-skinned tear fault. Additionally, we have calculated the strata shortening data for both Nos. 4 and 7 Faults to further our understanding of these systems. For No. 4 Fault, we observed shortening differences between the western and eastern sections in both the supra- and sub-salt strata, whereas for No. 7 Fault, we observed shortening differences only in the supra-salt strata. We demonstrated that under the action of thrusting, a tear fault could penetrate the salt layer if there is a shortening difference in the different positions of the sub-salt strata. A lack of shortening difference in the sub-salt strata implies that a tear fault should be thin-skinned which cannot penetrate the salt layer, even though the sub-salt strata may be deformed during thrusting.

Sedimentological features of the onshore Paleogene-Neogene Lawin Basin are of importance in better understanding the basin evolution and geodynamics. The N-S trending Lawin Basin, which is situated within the Western Belt of Peninsular Malaysia, is an extensional basin that formed during the sinistral movement of the Bok Bak Fault zone. This study evaluates the palaeodepositional environment, reveals the provenance, and interprets the transport dynamics of the mini-basin by integrating facies, petrographic, and grain size analyses. The basin lithologies can be broadly divided into conglomerate and sandy facies, with the former consisting of clast-supported conglomerate, matrix-supported conglomerate, cross-stratified pebble conglomerate, and bedded pebbly conglomerate, whereas the latter comprises massive pebbly sandstone, horizontally bedded sandstone, planar cross-bedded sandstone, and ripple laminated sandstone. The lithologies can be grouped into three main facies associations, including massive conglomerate, stratified conglomerate, and fluvial sandstone deposits, which reflect alluvial fan (debris/gravity flow deposits), braided gravel bar, and channel bar elements, respectively. Petrographic data indicate that the conglomerates are clast- and matrix-supported and were derived from a proximal source. The QFL range of detrital framework grains reveals that sandstones are composed of quartz (43–80 vol%), feldspar (9–54 vol%), and lithic fragments (2–16 vol%). The sandstones are coarse-grained, poorly-sorted, and sub-rounded to sub-angular in texture. They are arkose, sublitharenite, and lithic arkose in composition. QtFL/QmFLt ternary diagrams show that the sandstones are primarily derived from a provenance area comprising continental block material, including uplifted basement rocks and transitional continental deposits. This study proposes that the sandstones had a nearby granitic source (Bintang) and a debris source derived from recycled sedimentary rocks (the Baling Group sediments). Grain size parameters ranges (mean, −2.37 to 0.74 Φ; sorting, 1.22 to 2.07 Φ; skewness −0.21 to 0.91 Φ, kurtosis, 0.66 to 1.98 Φ, and average mean-sorting index of −0.24) are consistent with immature to sub-mature sedimentation deposited within a high-energy fluvial environment.

This research deals with the petrography and mineral chemistry of gabbroic and monzodioritic rocks to characterize the minerals, including their genesis and tectonic evolution. The rocks are dominated by gabbro in Barapaharpur and monzodiorite in Voktipur, and they contain plagioclase, hornblende, biotite, and magnetite, with few epidote and apatite, as well as clinopyroxene and orthopyroxene in gabbroic member. Chemical analyses of minerals were carried out by an electron microprobe analyzer. The chemistry of plagioclases is compositionally oligoclase-andesine and andesine, amphiboles are dominantly magnesiohornblende, biotites are Mg-biotites (phlogopite), and pyroxenes are diopside and enstatite types. The calculated P-T conditions of the gabbroic rocks yielded about 850–957 °C and 5.8–9.3 kbar, which are the highest geothermobarometric values in the region. However, the monzodioritic rocks yielded about 696–723 °C and 5.6–6.2 kbar. The estimated emplacement depths from the calculated highest pressure values equalize at ∼ 20–33 km and at ∼ 19–22 km, respectively. Biotite chemistry provides quantitative fO₂ within QFM and HM buffers ranging from −10.6 to −12.0 in gabbroic rocks and −11.6 to −13.5 in quartz monzodiorite, respectively. These data are also echoed by amphibole and pyroxene mineral chemistry, which collectively demonstrate that the source materials were in a relatively higher oxidation state within arc magmatism. The mineral data also offer calc-alkaline I-type suites formed within subduction-related environments. However, gabbroic rocks show a dominantly island arc signature substantiating the suprasubduction zone, and also have the affinity of the island arc tholeiitic and calc-alkaline basaltic equivalents within orogenic environments and marginally boninitic affinities.

Biogenic limestones from three sections (north, central, and south) across peninsular Italy have been analysed for major and trace elements and Nd, Pb, and Sr isotopic ratios. These data are used to monitor the evolution of the Tethys Ocean from the Triassic through to the Miocene. Limestones’ major, trace, and REE elements contents are consistent with their formation in seawater with little sign of crustal, volcanic, or hydrothermal input. V/Cr and Ce/Ce* ratios indicate their deposition in oxygenated waters. Rb-Sr-Ba discrimination diagram, consistent with the immobile trace element distribution, indicates that limestone deposition took place in either marginal or open ocean environments. Ages based on stratigraphy are in good agreement with the chronostratigraphic Sr curves implying that the Tethys ocean, throughout its history, was in contact with the open, global, ocean system. Although the isotopic values of Sr and Nd are relatively restricted, Pb is extremely variable and highly radiogenic. High Pb isotope ratios characterise limestones deposited during the rifting of the southern Tethyan ocean in the Lower Jurassic and in the Lower Cretaceous, suggesting stronger crustal inputs in small basins. The weighted average, present-day, isotope values (AIL = average Italian limestone) for the Italian limestones, excluding anomalous samples, are ⁸⁷Sr/⁸⁶Sr = 0.70785, ¹⁴³Nd/¹⁴⁴Nd = 0.51227, and ²⁰⁶Pb/²⁰⁴Pb = 18.94, ²⁰⁷Pb/²⁰⁴Pb = 15.69, ²⁰⁸Pb/²⁰⁴Pb = 38.66. These values are useful in monitoring the fate of limestones during orogenesis and the role that they may have played in magma genesis.

The surface trace of the East Zambales Fault (EZF) and its associated faults in the Lingayen Gulf have been previously mapped but no other characteristics were reported. This study utilized seismic reflection, multi-beam bathymetry, and side scan sonar to characterize the offshore EZF in terms of magnitudes of vertical displacement. Sequence stratigraphy and radiocarbon dates provided age constraints on the recurrence interval within the Holocene.

The EZF extends for ∼ 57 km into the gulf, follows a north-northwest trend, and bounds the karstic terrane (west) and fluvio-deltaic deposits (east). Sinistral motion is indicated by: 1) normal and reverse drag geometries, 2) reversal in the sense of throw with depth, 3) flower structure, and 4) right-stepping and the uplift of a pressure ridge named Pudoc Bathymetric High. The Central Lingayen Gulf Fault (CLGF), to the east of EZF, follows the same trend. The Lingayen Gulf Transverse Fault (LGTF), oriented east–west, forms a flower structure with the CLGF. The EZF, CLGF, and LGTF combined form the Lingayen Gulf Fault System, which divides the gulf into five fault blocks where uplift and subsidence locally occurred.

A paleo-delta at −60 m yielded an age of 6.8 kyBP, indicating it was formed during the first Holocene highstand. With natural compaction considered, fault-associated subsidence of 46–53 m may have occurred. The average Holocene vertical displacement is 2.1–2.2 m, which translates to a recurrence interval of 320–270 years for the fault system. The faults can likely generate earthquakes with magnitudes 7.5 (EZF), 6.7 (CLGF), and 6.6 (LGTF).

Northwestern Anatolia contains voluminous Cenozoic magmatic rocks which were emplaced during syn- to-post collisional stages of long-term crustal accretion and extensional stages since the late Paleocene. The Eocene to Late Miocene plutonic and volcanic rocks that are located throughout the Rhodopes, northern Aegean, and the western part of Western Anatolia show generally southward decreasing ages, coupled with an increasing crustal recycling component in their genesis. However, the early Eocene, ∼SW–NE-trending, mafic volcanic and the early Eocene, ∼NW-SE-trending, granitoid belts in the northeastern parts of Western Anatolia do not share these features. We present here new U-Pb zircon ages, whole-rock geochemical analyses, and Sr-Nd isotopic data from the early Eocene NW-SE-trending granitoid belt, together with age data from arc-related pyroclastics in the region, in an effort to resolve these uncertainties.

The age data reveal that the post-collisional magmatism along the ∼ NW–SE-trending granitoid belt occurred ∼ 58–41 Ma; i.e. ∼ 30 Myr after the Pontide arc magmatism that was active from ∼ 92–74 Ma. We suggest that the ∼ SW–NE-trending mafic volcanic and the ∼ NW-SE-trending granitoid belts developed in response to break-off of two subducted slabs in the northern Neotethys. In addition, emplacement of the ∼ NW-SE trending granitoid belt may also have been influenced by a zone of weakness related to a series of NW–SE-trending dextral strike-slip shear zones lying from the Kapıdağ shear zone close to the Rhodopes in the NW to the Uludağ shear zone in the SE.

The origin of active deformation and structural evolution in large areas of Western Borneo has been highly debated, with two contrasting views involving gravitational tectonics and plate tectonics. The scarcity of field data on land has significantly hampered our understanding of the onshore structures and their relationship with those of the offshore regions. The Baram Delta province is one of the best examples in SE Asia, where debates on the origin and evolution of active tectonic versus gravitational tectonic structures are broadly associated with the complexity of faults and folds in Brunei and Sarawak (Malaysia). In this paper, we present the results of the first large-scale satellite-based structural mapping and the detailed outcrop-based structural mapping in Brunei Darussalam. The results of the satellite-based mapping reveal a major ∼NE-SW trending detachment fault in Brunei and adjacent regions, which is termed the Tutoh fault, with numerous associated secondary faults and folds. The fault acts as a detachment structure onto which several NW-SE trending faults ramp and have asymmetrical folds showing an en echelon fold-fault system. The topographic expression and the recent strike-slip faulting event on the Tutoh fault system suggest that the fault remains active, challenging the discourse that gravitational tectonics is the only cause of active deformation in Borneo.