Search results for "Geophysic"

Variation of olivine composition in the volcanic rocks in the Songliao basin, NE China: lithosphere control on the origin of the K-rich intraplate ma…

2016

Abstract Lithospheric thickness and the heterogeneity of the mantle lithosphere are two major parameters that play a role in determining the final composition of the mafic melts and their minerals. The Songliao basin in northeast China represents an ideal natural laboratory to study the effect of these two parameters on early Pliocene to Holocene K-rich mafic lavas (K2O > 4 wt.%; K2O/Na2O > 1). A series of Cenozoic volcanic edifices (Erkeshan, Wudalianchi, Keluo and Xiaogulihe) are tentatively divided into three groups (Group 1 — thin, Group 2 — middle, and Group 3 — thick) according to the lithosphere thickness. They are located in the northern region of the Songliao basin extending in a n…

Zircon ages and Hf isotopic compositions of Ordovician and Carboniferous granitoids from central Inner Mongolia and their significance for early and …

2016

Abstract We present zircon ages and Hf-in-zircon isotopic data for plutonic rocks and review the evolution of central Inner Mongolia, China, in the early and late Paleozoic. Zircons of a granodiorite yielded a 206 Pb/ 238 U age of 472 ± 3 Ma that reflects the time of early Paleozoic magmatism. Zircon ages were also obtained for a tonalite (329 ± 3 Ma), quartz-diorite (320 ± 3 Ma), and granite vein (297 ± 2 Ma). Our results, in combination with published zircon ages and geochemical data, document distinct magmatic episodes in central Inner Mongolia. The dated samples are mostly granodiorite, tonalite and quartz-diorite in composition with intermediate to high-silica, high Na 2 O (3.08–4.26 w…

Serbo-Macedonian revisited: A Silurian basement terrane from northern Gondwana in the Internal Hellenides, Greece

2009

Abstract New geochronological and geochemical data on basement orthogneisses from the Vertiskos Unit of the Serbo-Macedonian Massif (SMM), Internal Hellenides, northern Greece, are used in order to constrain the pre-Alpine tectonic history of the basement units in the metamorphic hinterland of the Hellenides. The prevailing rock types in the Vertiskos crystalline basement are coarse-grained biotite augengneisses with subordinate leucocratic muscovite gneisses and two-mica gneisses. Zircon Pb–Pb and U–Pb ages on 20 samples range from 425.9 ± 4.2 Ma to 443.4 ± 5.5 Ma with a mean of 432.2 ± 3.2 Ma and are interpreted as primary crystallisation ages of the basement granites on the basis of the …

A fault-related coalification anomaly in the Blanzy-Montceau Coal Basin (Massif Central, France)

1997

Abstract The Stephanian intramontane Blanzy-Montceau Coal Basin is situated along a Variscan fault complex bordering the Upper Paleozoic Blanzy-Le Creusot-Bert graben. The deposition of coal-bearing strata was controlled by a complex of early faults known as the “Faille de Bordure” (FB, Border Fault). Another complex of Permian faults known as the “Faille de l'Est” (FE, Eastern Fault) is situated along the more central part of the coal basin. Coalification in the basin follows three main trends: (1) Increasing rank from upper to lower coal seams in accordance with a general vertical trend (Hilt, 1873). The gradient of volatile matter is higher than normal, ranging from 3% to I I% Vdaf per 1…

2021

Abstract. Lignin oxidation products (LOPs) are widely used as vegetation proxies in climate archives, such as sediment and peat cores. The total LOP concentration, Σ 8, provides information on the abundance of vegetation, while the ratios C / V and S / V of the different LOP groups also provide information on the type of vegetation. Recently, LOP analysis has been successfully applied to speleothem archives. However, there are many open questions concerning the transport and microbial degradation of LOPs on their way from the soil into the cave system. These processes could potentially alter the original source-dependent LOP signals, in particular the C / V and S / V ratios, and thus compli…

A regional-scale discontinuity in western Sicily revealed by a multidisciplinary approach: A new piece for understanding the geodynamic puzzle of the…

2015

The results of an integrated stratigraphic, structural, geophysical, and geochemical study reveal the presence of a crustal discontinuity in western Sicily that, at present, runs roughly N-S along a band from San Vito Lo Capo to Sciacca (SVCS). The boundary between the two zones of this discontinuity is nearly orthogonal to the main thrust propagation of the Sicilian thrust-and-fold belt. The different Permian to Tertiary sedimentary evolution recorded by the two zones appears related to this discontinuity, with thick carbonate platforms in the western sector facing deep-water successions in the eastern one. The presence of Upper Triassic reefs, huge megabreccias bodies, and widespread subm…

The most ancient ophiolite of the Central Asian fold belt: U–Pb and Pb–Pb zircon ages for the Dunzhugur Complex, Eastern Sayan, Siberia, and geodynam…

2002

Abstract Ophiolitic rocks with a zircon age of ∼1020 Ma occur in the Dunzhugur complex of East Sayan, Siberia, and are part of a Neoproterozoic to early Palaeozoic segment of the Central Asian fold belt. The most spectacular suite is exposed along the Oka and Bokson rivers, where a complete ophiolite sequence with mantle tectonites, a layered sequence composed of dunite, wehrlite, and pyroxenite, a gabbro section, a sheeted diabase dyke complex and basaltic pillow lavas are exposed. Petrologic and geochemical data suggest that all members of the ophiolite originally belonged to the same cogenetic mafic–ultramafic crustal section and support a supra-subduction zone setting in a fore-arc rift…

Surface expression of eastern Mediterranean slab dynamics: Neogene topographic and structural evolution of the southwest margin of the Central Anatol…

2012

[1] The southwest margin of the Central Anatolian Plateau has experienced multiple phases of topographic growth, including the formation of localized highs prior to the Late Miocene that were later affected by wholesale uplift of the plateau margin. Our new biostratigraphic data limit the age of uplifted marine sediments at the southwest plateau margin at 1.5 km elevation to <7.17 Ma, and regional lithostratigraphic correlations imply that the age is <6.7 Ma. Single-grain CA-TIMS U-Pb zircon analyses from a reworked ash within the marine sediments yield dates as young as 10.6 Ma, indicating a maximum age that is consistent with the biostratigraphy. Our structural measurements within the upl…

Tectonic beheading of fluvial valleys in the Maestrat grabens (eastern Spain): Insights into slip rates of Pleistocene extensional faults

2013

Abstract Interaction between faulting and landscape evolution in regions of active tectonics allows us to use subtle geomorphological markers for estimating fault slip rates. Geomorphic features of two valleys connected with the bottom of the Alcala de Xivert graben, at the Maestrat graben system (eastern Spain), suggest that they correspond to the lowest segments of ancient valleys whose original heads were located at the axis of the neighbouring Irta range. They were beheaded owing to displacement of the Torreblanca and Irta faults during a period of active extensional faulting in Middle Pleistocene times. These faults produced a negative inversion of the relief, sinking a narrow graben (…

Middle-Late Pleistocene marine terraces and fault activity in the Sant’Agata di Militello coastal area (north-eastern Sicily)

2012

Abstract The coastal sector of Sant’Agata di Militello (north-eastern Sicily) is characterized by a flight of raised Middle-Upper Pleistocene marine terraces occurring at different heights with respect to present sea level. In particular, the geomorphological survey and the analysis of stereo-pairs of aerial photographs allowed to recognize at least five main orders of well preserved Quaternary surfaces and relative deposits mostly located at the hanging wall and at the footwall of the Pleistocene northwest-dipping Capo d’Orlando normal fault, which controlled the geomorphological evolution of the coastal area. The marine terraces show an overall good morphological continuity and are formed…