Tectonic Implications Research Articles

Geochemical characteristics and tectonic implications of igneous rocks from the Santos Basin and adjacent areas

Geochemical characteristics and tectonic implications of igneous rocks from the Santos Basin and adjacent areas

Alkaline-rich intermediate and felsic melts beneath the NW Iranian plate: new insights from coeval silica-undersaturated and -saturated rocks

ABSTRACT New whole-rock major and trace element data, coupled with Sr–Nd isotopic ratios data, zircon Hf isotopes, and U–Pb geochronology are presented for three alkaline intrusions (Hashroud, Sisan, and Sarab) in the Zanjan-Takab complex in northwestern Iran, to investigate their sources, petrogenesis, and tectonic implications of emplacement. The Hashroud and Sisan plutons are mainly composed of silica-saturated granite and syenogranite, respectively, whereas the Sarab region consists of nepheline-bearing syenite, and associated undersaturated lavas ranging in composition from tephri-phonolite to trachy-basalt/andesite. Zircon U–Pb geochronology gives emplacement ages of 38 and 36 Ma for the Hashroud and Sisan silica-saturated rocks, which are slightly younger than the Sarab silica-undersaturated rocks (40 Ma). Silica-undersaturated and silica-saturated rocks differ from each other mostly in terms of their silica content, but show comparable incompatible trace element distributions, typical of subduction-related magmatic rocks. The undersaturated rocks display higher LILE/HFSE (Ba/Th: up to 365), but relatively similar LILE/LREE (Ba/La: 13–44) values to those of saturated rocks (Ba/Th: up to 38; Ba/La: up to 27). Silica-undersaturated and -saturated rocks also show distinct Sr–Nd–Pb isotopic compositions, with the former having less radiogenic Sr (87Sr/86Sr, 0.70452–0.70510) and Pb (206Pb/204Pb, 18.61–18.67; 207Pb/204Pb, 15.57–15.60; 208Pb/204Pb, 38.64–38.74) and more radiogenic Nd (143Nd/144Nd, 0.512648–0.512674) than the latter (87Sr/86Sr, 0.70619–0.71409; 206Pb/204Pb, 18.78–18.82; 207Pb/204Pb, 15.60–15.63; 208Pb/204Pb, 38.78–38.82; 143Nd/144Nd, 0.512613–0.512620). Geochemical and isotopic compositions of the silica-undersaturated rocks suggest the involvement of fluids derived from subducted oceanic crust and subordinate sediment as metasomatizing agents in their mantle source. On the other hand, the studied silica-saturated units, which crystallized from mafic parental melts modified by crustal assimilation and fractional crystallization, originated from a lithospheric mantle source that had been metasomatized via a relatively high volume of terrigenous subducted sediment melts. Both the Eocene saturated and undersaturated igneous rocks formed in a post-collisional extensional setting. Our study, along with compiled data, also finally settles the long-standing debate about the geodynamic evolution of the NW Iranian belt, showing that a compressive to extensional tectonic regime existed during the Arabia–Eurasia collision. This was related to the Neo-Tethyan slab roll-back, which generated alkali-rich magmatic rocks throughout the NW Iranian belt.

Seismic Structure of Singapore: Implications for Tectonics, Geothermal Energy Utilization, and Seismic Hazard Estimation

Abstract High-precision urban subsurface geophysical imaging is critical for city development, including urban construction, seismic hazard assessment, and renewable energy development. We investigate the top 5 km VS, sediment thickness, Moho depth, and crustal average VP/VS of Singapore using teleseismic P-wave polarizations and receiver functions from a nodal array and some permanent stations. We present the first sediment model of Singapore, which shows the thickest compacted sediments (∼1.2 km) in the west, negligible sediments in central area and some localized sediments in the east (∼0.8 km) and northwest (∼1.1 km). Based on the new crustal model and previous geological surveys, we discuss a possible tectonic evolutionary history of Singapore, which is related to the subduction of the Paleo-Tethys slab. The observed low-VS anomaly beneath the Sembawang hot spring reveals its possible deep heat source, indicating a potential source of geothermal energy in Singapore. In addition, ground-motion amplification variations caused by local site conditions across Singapore are estimated, showing that areas of soft sediment, especially the reclaimed land in the east, have the highest seismic risk.

Late Quaternary left-slip rate of the Dangjiang segment along the Ganzi-Yushu-Xianshuihe Fault Zone in the central Tibetan Plateau and the tectonic implications

Late Quaternary left-slip rate of the Dangjiang segment along the Ganzi-Yushu-Xianshuihe Fault Zone in the central Tibetan Plateau and the tectonic implications

Thermal-tectonic history of the İspir-Ulutaş porphyry Cu-Mo deposit, Eastern Pontides: Implications for regional tectonics and exploration of porphyry systems

Thermal-tectonic history of the İspir-Ulutaş porphyry Cu-Mo deposit, Eastern Pontides: Implications for regional tectonics and exploration of porphyry systems

Hydrogeochemical characteristics of hot springs in the Longriba fault, northeastern Tibetan Plateau: Tectonic implications for geothermal fluid circulation

Hydrogeochemical characteristics of hot springs in the Longriba fault, northeastern Tibetan Plateau: Tectonic implications for geothermal fluid circulation

Petrogenesis and tectonic implications of blueschist-facies garnet-mica schist in the Dabie orogenic belt, central China

Petrogenesis and tectonic implications of blueschist-facies garnet-mica schist in the Dabie orogenic belt, central China

Provenance and tectonic implications of Quaternary sediments of the Min River in the southeastern margin of the Tibetan Plateau

Provenance and tectonic implications of Quaternary sediments of the Min River in the southeastern margin of the Tibetan Plateau

Holocene activities and tectonic implications of the Da’an-Dedu Fault Zone in the Songliao Basin, NE China

Holocene activities and tectonic implications of the Da’an-Dedu Fault Zone in the Songliao Basin, NE China

Petrogenesis and tectonic implications of Neoarchean mafic and felsic rocks in western Liaoning: Constraints on the crustal evolution of the northeastern North China Craton

Petrogenesis and tectonic implications of Neoarchean mafic and felsic rocks in western Liaoning: Constraints on the crustal evolution of the northeastern North China Craton

Sedimentary Provenance Transition in the North Yellow Sea Basin During Tectonic Transition Period of the Eastern North China Craton in the Late Mesozoic and Its Tectonic Implications

Sedimentary Provenance Transition in the North Yellow Sea Basin During Tectonic Transition Period of the Eastern North China Craton in the Late Mesozoic and Its Tectonic Implications

Detrital zircon U–Pb geochronology of the Murree Formation, western Himalaya, Pakistan: provenance and tectonic implications for Himalayan exhumation

ABSTRACT The Murree Formation is the oldest continental sequence in the Himalayan foreland basin and holds significant information about the Himalayan exhumation following the India-Asia collision. This study explains the provenance of the Murree Formation using detrital zircon U-Pb geochronology supplemented with sandstone petrography to unravel the Himalayan exhumation in Pakistan. The sandstone provenance indicates the sediment was sourced from recycled orogen and suture belts, supporting a post-collisional origin. The source rocks, shown by the ternary plot (QpQnuQu), comprise plutonic and medium to high-rank metamorphic rocks prevalent in the Higher Himalaya (HH), Tethyan Himalayan (TH), and Lesser Himalaya (LH). The zircon ages are mainly ~ 1200–400 Ma, with two minor clusters (~1900–1400 Ma and ~ 2600–2300 Ma). This pattern is compatible with a Himalayan source mainly from the TH, HH, and partly from LH. Notably, the age populations < 200 Ma are in minor percentages, which indicates the hindrance from the Kohistan – Ladakh Arc (KLA) (Asian source) to the foreland basin due to the uplift of the TH and HH blocks. Combining the petrography and zircon U – Pb geochronology, a tectonic model is proposed, which suggests fold – thrust belt propagation to the south after the India – Asia collision. During the deposition of the Murree Formation in the foreland basin, TH and HH blocks were already uplifted in the western Himalaya, which provided major detritus. Along with this significant contribution, a minor contribution from a part of the LH is also suggested. This suggestion is based on the presence of Cambro – Ordovician detrital zircon ages, mainly from the plutonic source indicative of erosion of the Cambro – Ordovician granites and metamorphic rocks due to the initial phase of uplift along the Panjal fault.

Identification of the Shuanglongtan tectonic mélange (ca. 1.7–1.5 Ga) in the southwestern Yangtze Block and it’s tectonic implications

Identification of the Shuanglongtan tectonic mélange (ca. 1.7–1.5 Ga) in the southwestern Yangtze Block and it’s tectonic implications

High-K, I-type Tonian post-collisional magmatism in the South Delhi Terrane, NW India: Petrogenetic and tectonic implications

High-K, I-type Tonian post-collisional magmatism in the South Delhi Terrane, NW India: Petrogenetic and tectonic implications

Geochemistry and mineralogy of the late Neogene alkaline megalake sediments in the Qaidam Basin (China): Implications for provenance, tectonics, paleoclimate, paleoenvironment and organic matter accumulation

Geochemistry and mineralogy of the late Neogene alkaline megalake sediments in the Qaidam Basin (China): Implications for provenance, tectonics, paleoclimate, paleoenvironment and organic matter accumulation

Origin, petrogenesis and tectonic implications of the Jiasha potassic intrusive complex in the giant Gejiu Sn Cu polymetallic field, SW China

Origin, petrogenesis and tectonic implications of the Jiasha potassic intrusive complex in the giant Gejiu Sn Cu polymetallic field, SW China

Petrogenesis and tectonic implications of Paleozoic S-type granitic gneisses of Nanga Parbat Syntaxis, North Pakistan

Petrogenesis and tectonic implications of Paleozoic S-type granitic gneisses of Nanga Parbat Syntaxis, North Pakistan

Identifying topographic disequilibrium conditions and their lithological and tectonic implications in a rifted river basin of Eastern India: Insights from DEM-derived longitudinal profiles and their derivatives

Identifying topographic disequilibrium conditions and their lithological and tectonic implications in a rifted river basin of Eastern India: Insights from DEM-derived longitudinal profiles and their derivatives

Petrography and geochemistry of the Dupi Tila formation: Implications for depositional environment and tectonics

Petrography and geochemistry of the Dupi Tila formation: Implications for depositional environment and tectonics

Mineralogy and Geochemistry of Upper Cretaceous-Pliocene Sedimentary Rocks in the Yahşihan Basin, Central Anatolia, Türkiye: Provenance and Tectonic Implications

The Yahşihan/Kırıkkale sedimentary basin, located in Central Anatolia within the İzmir-Ankara-Erzincan suture zone, mostly consists of Upper Cretaceous to Lower Pliocene sediments developed on the Ankara Melange, which is linked to the Northern Neo-Tethys Ocean. Although the stratigraphic, sedimentological, and tectono-stratigraphic characteristics of the basin have been investigated by many researchers, its mineralogical and geochemical characteristics have not been studied extensively. In this study, the provenance, paleoclimatological properties, and tectonic structure of the sedimentary rocks were interpreted using detailed mineralogical and geochemical analysis data. Formations such as the Karadağ (Cenomanian-Campanian), Çiçekdağ (Santonian-Campanian), Samanlık (Maastrichtian), Dizilitaşlar (Paleocene-Early Eocene), Çayraz (Middle Eocene), İncik (Upper Eocene-Lower Miocene), Central Anatolia Group (Middle Miocene-Pliocene), and Quaternary alluvium were deposited in the basin. X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), and geochemical analyses were employed to determine the mineralogical and chemical composition of the units. Although highly oxic paleo-environmental conditions predominated in the basin, anoxic and suboxic conditions could also be present in the Dizilitaşlar and İncik formations. The units are primarily felsic with some mafic contributions, suggesting an oceanic island arc environment with varying paleoenvironmental conditions, reflecting seasonal changes between humid and arid periods.