Search

Paleomagnetic and geochronological studies were carried out on a ∼ 450 km long (from 17 sites) N-S striking Paleoproterozoic dyke swarm exposed along a natural crustal cross section of about 10 km (increasing from North to South) in the Dharwar Craton, to study the characteristics of paleomagnetism and geochronology in vertical dimension. U-Pb/Pb-Pb dating on baddeleyite gives a crystallisation age of 2216.0 ± 0.9 Ma for long dyke AKLD. Paleomagnetic data from this well dated ∼ 2216 Ma dyke swarm in Dharwar Craton are of excellent quality. High coercivity and high blocking temperature components are carried by single domain magnetite and show dual polarity remanence directions. Combined normal and reverse polarity remanences on AKLD and other N-S dykes define the most reliable paleomagnetic pole for ∼ 2216 Ma at latitude 36°S and longitude 312°E (A95 = 7°). Though paleomagnetic data is unavailable on other N-S dykes below the Cuddapah basin, high precision geochronology suggest that they are of similar age within errors. Though there is a variation in the crustal depth of Dharwar craton from north to south, consistent Pb-Pb/U-Pb baddeleyite geochronology and paleomagnetic studies along the AKLD established its continuity and preservation along its entire strike length. The virtual geomagnetic poles of these sites confirm a stable remanence and are almost identical to the previously reported paleomagnetic pole and also supported by positive reversal test. Positive paleomagnetic reversal test on these dykes signify that the remanent magnetization is primary and formed during initial cooling of the intrusions. Updated apparent polar wander path of Dharwar craton indicates relatively low drift rate during 2.21–2.08 Ga interval. Magnetogranulometry and SEM studies show that remanent magnetization in this dyke was carried by single domain magnetite residing within silicate minerals. [ABSTRACT FROM AUTHOR]

Introduction: A congenitally absent Inferior Vena Cava (IVC) is a rare anomaly that is recognised to be associated with idiopathic Deep Venous Thrombosis (DVT), particularly in the young. It may not be apparent until later in life. Retrospectively, as discussed in this case, there can be clues indicating the presence of such an anomaly from a young age. However, it is not clear whether early recognition of this condition would affect the prognosis and treatment., Case Presentation: A 54 year old gentleman was admitted with 3 weeks of abdominal pain and localised swelling over the right flank. Examination revealed palpable 'snake-like' tortuous, tender lumps on the abdominal wall. Past history revealed chronic non-healing venous leg ulcers, and varicose veins necessitating varicose vein ligation at a very young age. The ulcers eventually needed skin grafting.During this, current admission he was investigated and diagnosed with Deep Vein Thrombosis (DVT). CT scan, performed to search for intra-abdominal cancer, revealed absence of the Inferior Vena Cava with extensive thrombosed collaterals of the superficial abdominal and azygous veins and a congenitally atrophic left kidney., Conclusion: This is a case of one of the oldest patient described in the literature to be diagnosed with absence of the IVC. It is thought that IVC anomalies are under-diagnosed, and may be commoner than once believed. However there were vital clues in his previous medical history suspicious for an underlying venous anomaly. Idiopathic DVT in a relatively young person with a past history of chronic leg ulceration or varicose veins should be investigated for congenital anomalies of the IVC. This is best achieved by CT scan of the abdomen.