Search results for "Basement"
showing 10 items of 152 documents
U-Pb and Pb-Pb zircon ages for metamorphic rocks in the Kaoko Belt of Northwestern Namibia: A Palaeo- to Mesoproterozoic basement reworked during the…
2004
The Kaoko Belt belongs to the Neoproterozoic mobile belt system of western Gondwana, whose geodynamic evolution is assumed to have resulted from collision between the Congo Craton (present Africa) and the Rio de la Plata Craton (present South America). Several magmatic intrusion periods can be distinguished in the coastal area of this belt, based on conventional U-Pb, SHRIMP and Pb-Pb evaporation analyses on zircons. The prevailing igneous rock types are of granitic to tonalitic composition. A Palaeoproterozoic terrain with U-Pb magmatic emplacement ages between ~2.03 and 1.96 Ga may be correlated with the Eburnian event (~1.8 to 2.0 Ga), which is widespread in Africa. Additionally, two dis…
Tectonothermal Evolution of the Broadly Rifted Zone, Ethiopian Rift
2019
The Broadly Rifted Zone (BRZ) of southern Ethiopia is a long-lived and structurally complex segment of the East African Rift System. However, due to poor surface exposure of early synrift strata and a dearth of subsurface data, the evolution of the BRZ remains poorly understood. We present new apatite (U-Th-Sm)/He and augmented apatite fission track low-temperature thermochronology data from the Beto and Galana basin boundary fault systems to constrain the tectonothermal evolution of the western and eastern BRZ, respectively. Time-temperature reconstructions suggest that East African Rift System-related extension began concurrently across the BRZ in the early Miocene (20–17 Ma), at least 6 …
Nearshore, temperate, carbonate depositional systems (lower Tortonian, Agua Amarga Basin, southern Spain): implications for carbonate sequence strati…
1997
Abstract The bryozoan-rich lower Tortonian carbonates of the Agua Amarga Basin in southern Spain (Province of Almeria) provide an example of sediments formed in a nearshore, non-tropical depositional setting. Based on data derived from logging of sections and from field mapping, these lower Tortonian carbonates form a depositional sequence, which is subdivided into several depositional systems. A lowstand systems tract, which consists of volcaniclastic fan deltas and washover deposits, formed on the leeward side of a basement shoal which delimited the basin towards the south. A transgressive systems tract, which is characterised by a landward encroachment of deposits, is represented by subm…
Eclogites within the Menderes Massif / western Turkey
1997
Metagabbros in the core series of the Menderes Massif, for some time considered as post orogenic Miocene intrusives, revealed a strong poly-metamorphic history. The metagabbro bodies exhibit a pronounced zonation. Within their cores, igneous minerals are still preserved. Coronitic textures are interpreted as results of a high temperature, possibly granulitic overprint. The outer parts of the metagabbro bodies mostly consist of strongly to completely retrograded gamet-amphibo-lites, but occasionally contain relies of eclogites. Petrologic investigations confirmed a high pressure overprint and allowed preliminary P, T estimates (650 degrees C, equal to or greater than 1.3 GPa). The intensity …
The southern margin of the Caribbean Plate in Venezuela: tectono-magmatic setting of the ophiolitic units and kinematic evolution
2002
Abstract The southern Caribbean Plate margin in Venezuela consists of a W–E elongated deformed belt, composed of several tectonic units dismembered along the northern part of the South America continental Plate since the Late Cretaceous. The present review, based on petrology and tectono-magmatic significance of each unit, makes it possible to define the main geotectonic elements and to reconstruct the paleogeographic domains from Late Jurassic to Tertiary: (a) Mid-Ocean Ridge Basalt (MORB) proto-Caribbean oceanic basin (Loma de Hierro Unit); (b) oceanic plateau (Dutch and Venezuelan Islands basement); (c) rifted continental margin (Cordillera de La Costa and Caucagua–El Tinaco Units) with …
Phosphorylation of the Goodpasture antigen by type A protein kinases.
1995
Collagen IV is the major component of basement membranes. The human alpha 3 chain of collagen IV contains an antigenic domain called the Goodpasture antigen that is the target for the circulating immunopathogenic antibodies present in patients with Goodpasture syndrome. Characteristically, the gene region encoding the Goodpasture antigen generates multiple alternative products that retain the antigen amino-terminal region with a five-residue motif (KRGDS). The serine therein appears to be the major in vitro cAMP-dependent protein kinase phosphorylation site in the isolated antigen and can be phosphorylated in vitro by two protein kinases of approximately 50 and 41 kDa associated with human …
Type IV collagen and laminin in slow and fast skeletal muscle in rats--effects of age and life-time endurance training.
1988
The changes in the biochemical composition of basement membrane (BM) in slow-twitch (m. soleus, MS) and fast-twitch (m. rectus femoris, MRF) skeletal muscles of rats were studied during aging and life-time endurance training (treadmill running). The concentrations of the 7S domain of type IV collagen and of the P2 fragment of laminin were determined with radioimmunoassays in the muscles of rats aged 1, 2, 4, 10, and 24 months. The concentration of type IV collagen was higher in MS than in MRF and increased significantly with age. At older ages, the concentration tended to be higher in the MS of trained than untrained rats. The concentration of laminin was significantly higher in MRF than in…
Cross-reactivity of anti-ssDNA antibodies with heparan sulfate in patients with type I diabetes mellitus
1989
Anti-single-stranded–DNA antibodies cross-reactive with heparan sulfate were detected in serums of patients with type I (insulin-dependent) diabetes mellitus. The results suggested that heparan sulfate, the major glycosaminoglycan constituent of the glomerular basement membrane, may serve as a target antigen in vivo for cross-reactive anti-DNA antibodies. These polyreactive antibodies, directed toward repeating negatively charged units, may neutralize the heparan sulfate–associated polyanionic sites in the glomerulus, leading to an abnormal permeability of anionic plasma proteins.
Acute exercise induced changes in rat skeletal muscle mRNAs and proteins regulating type IV collagen content
2001
This experiment tested the hypothesis that running-induced damage to rat skeletal muscle causes changes in synthesis and degradation of basement membrane type IV collagen and to proteins regulating its degradation. Samples from soleus muscle and red and white parts of quadriceps femoris muscle (MQF) were collected 6 h or 1, 2, 4, or 7 days after downhill running. Increased muscle β-glucuronidase activity indicated greater muscle damage in the red part of MQF than in the white part of MQF or soleus. In the red part of MQF, type IV collagen expression was upregulated at the pretranslational level and the protein concentration decreased, whereas matrix metalloproteinase-2 (MMP-2), a protein th…
Regulation of glomerular basement membrane collagen expression by LMX1B contributes to renal disease in nail patella syndrome.
2001
Basement membrane (BM) morphogenesis is critical for normal kidney function. Heterotrimeric type IV collagen, composed of different combinations of six alpha-chains (1-6), is a major matrix component of all BMs (ref. 2). Unlike in other BMs, glomerular BM (GBM) contains primarily the alpha 3(IV) and alpha 4(IV) chains, together with the alpha 5(IV) chain. A poorly understood, coordinated temporal and spatial switch in gene expression from ubiquitously expressed alpha 1(IV) and alpha 2(IV) collagen to the alpha 3(IV), alpha 4(IV) and alpha 5(IV) chains occurs during normal embryogenesis of GBM (ref. 4). Structural abnormalities of type IV collagen have been associated with diverse biological…