Time filter

Source Type


Rajesh H.M.,BIUST | Santosh M.,China University of Geosciences | Wan Y.,Chinese Academy of Geological Sciences | Liu D.,Chinese Academy of Geological Sciences | And 2 more authors.
Precambrian Research | Year: 2014

SHRIMP U-Pb analysis of zircon grains from an ultrahigh temperature Mg-Al granulite from the northern margin of the Kaapvaal Craton (Southern Marginal Zone) shows ages of ~2.72. Ga for the peak metamorphism. Geochemical characteristics of syn-tectonic charnockites in the area are similar to magnesian charnockites, typically formed in subduction settings. In contrast to the prevailing models on peak metamorphism in the context of Neoarchean continent collision between Archean Zimbabwe and Kaapvaal cratons resulting in the formation of the Limpopo Complex, we relate the Neoarchean events to the accretion of this marginal block to the rest of the Kaapvaal Craton. In this model, the subduction event is marked by the formation of magnesian charnockites, and the ultrahigh temperature metamorphism dates the collision event. © 2014 Elsevier B.V. Source

Yang Q.-Y.,China University of Geosciences | Santosh M.,China University of Geosciences | Santosh M.,Kochi University | Rajesh H.M.,BIUST | And 2 more authors.
Lithos | Year: 2014

Charnockites (pyroxene-bearing granitoids) of magmatic origin in diverse tectonic settings and ranging in age from Mesoarchean to Cretaceous constitute important components of the continental crust. Here we report charnockites displaying both magnesian and ferroan compositions associated with gabbros from an AMCG (anorthosite-mangerite-charnockite-granite) suite in the North China Craton. The orthopyroxene in the magnesian charnockite is characterized by moderate XMg of 0.63-0.65 (Wo1-2En62-63Fs35-36), and low Al2O3 content of 0.59-0.71wt.%. The magnesian charnockites show medium- to high-K contents, and high Mg# (~47-69) similar to that of gabbros, whereas the Mg# of the ferroan charnockites is low (~6-28). The ferroan charnockites are alkali-calcic to alkalic, and weakly peralkaline to metaluminous, whereas the magnesian charnockites are calcic to calc-alkalic, and metaluminous. Although magnesian charnockites are in general considered to have formed in subduction setting, the medium- to high-K contents, high Mg# values with a wide range, and the highly negative εHf values of the zircons in these rocks (-8. 4 to -13.6), suggest inheritance of the arc signature from the melting of ancient arc-related crustal material. The ferroan charnockites show tholeiitic affinity and define a common differentiation trend with the gabbroic anorthosites and likely represent fractionated end-members with or without crustal interaction in a post-collisional rift setting. We present U-Pb age data from zircon grains on seven samples including two ferroan charnockites, three magnesian charnockites, one gabbroic enclave in magnesian charnockite and one gabbroic anorthosite which show emplacement ages of 1748.8 ± 6.4Ma, 1747.1 ± 9.5 Ma, 1756.4 ± 7.3 Ma, 1756.7 ± 9.2 Ma, 1731 ± 17 Ma, 1731.6 ± 8.2 Ma and 1746.5 ± 7.3 Ma respectively. The negative εHf values (-1.2 to -13.6) of zircon grains from these rocks and the older crustal model ages ranging from Mesoarchean to Paleoproterozoic suggest that the magma sources of these rocks involved the melting of ancient crustal components. The age data suggest that the magmatic suite was emplaced within a relatively short time interval between1.73 and 1.76Ga, during late Paleoproterozoic, placing the rocks suite in a post-collisional scenario, following the amalgamation between the Eastern and Western Blocks of the North China Craton along the Trans-North China Orogen at ca. 1.85-1.80Ga. © 2014 Elsevier B.V. Source

Selvaraj R.,BIUST | Kuthadi V.M.,University of Johannesburg | Marwala T.,University of Johannesburg
IET Communications | Year: 2016

Nowadays, distributed denial of service (DDoS) becomes a major challenge in the network as it affects the network at multi-level. This leads to traffic overhead and wastage of bandwidth utilisation. In order to overcome these issues, ant-based DDoS detection technique using roaming virtual honeypots is proposed. In this technique, virtual roaming honeypot along with the multi-level secure architecture is used to collect the information about the various intruders at different levels in the network. Ant colony optimisation technique is used to detect the intruders based on the pheromone deposit on that considered area. A multi-level IP log table is used to detect the intruders at different levels of the network. Once the affected area is found, the information is sent to multi-level architecture to limit the spread of the affected area to the honeypot. This information is sent to the honeypot to make a defence system against the attackers. The advantage of the proposed technique is that it provides a full defence against DDoS at multi-level without creating any traffic overhead. © The Institution of Engineering and Technology 2016. Source

Franchi F.,BIUST | Franchi F.,CNR Institute of Neuroscience | Franchi F.,University of Bologna | Hofmann A.,University of Johannesburg | And 4 more authors.
Chemical Geology | Year: 2015

Petrological and geochemical analyses were carried out on Early Devonian Kess Kess mound limestones of the Seheb el Rhassel Group exposed in the Hamar Laghdad Ridge (Tafilalt Platform, Eastern Anti-Atlas, Morocco) in order to evaluate marine vs hydrothermal processes for the origin of the mounds. Hydrothermal fluid circulation affected limestone deposition resulting in the formation of a plumbing system preserved in the mound facies and inter-mound facies as cavities, veins, and dykes.Shale-normalized rare earth element (REE) patterns for limestones display pronounced light REE depletion compared to middle REE (average PrSN/DySN=0.46) and heavy REE (average PrSN/YbSN=0.55), a super-chondritic Y/Ho ratio (up to 87) and positive La anomaly consistent with precipitation from normal marine seawater. Within our data set the Ce anomaly, as well as U and other trace element concentrations vary with facies providing evidence for variable redox conditions. The presence of positive Ce anomaly in carbonates of the plumbing system is consistent with precipitation under anoxic condition. Samples from mound facies and quartz veinlets in the upper part of the group show REE patterns consistent with precipitation from hydrothermal fluids.Early Devonian hypothetical seawater REE patterns were calculated from samples showing normal marine REE patterns (i.e. inter-mound facies) and from samples with weaker marine signature (i.e. fossiliferous mound limestones and plumbing system deposits). Hypothetical patterns are slightly enriched in σREE compared to modern open ocean seawater.This study reveals that REE analysis is a powerful tool for understanding polygenetic carbonate systems. It sheds light into the genesis of the Kess Kess mounds by reconstructing fluid pathways and palaeo-redox conditions. © 2015 Elsevier B.V. Source

Kuthadi V.M.,University of Johannesburg | Selvaraj R.,BIUST | Marwala T.,University of Johannesburg
Advances in Intelligent Systems and Computing | Year: 2016

Numerous schemes for data aggregation are done by encryption for privacy of data, and thus, homomorphism has been reviewed and designed on the wireless sensor network (WSN) to improve security. WSN is an emerging and challenging technology in the area of the research because of its vital scope with low power energy associated with it. Several application sensors collect information or data from different sensed nodes and will be aggregated to a host computer or a base station. Data aggregation happens in a network between intermediate nodes which causes to reduce energy consumption on these nodes to make efficient network performance. The algorithm used in existing aggregation system does not provide sufficient security functionality and is more vulnerable to several attacks. Furthermore, some compromised nodes also inject false data which leads to a falsify data aggregation which is forwarded to base station. The enlargement of WSNs is thrombosed due the limited energy constraints. The main focus of this paper is done mainly on enhancing energy in WSN by working on the enhancement of some routing protocol. This paper also explains on eliminating of data vulnerability, security aggregation, and false data injecting attack by presenting different robust surveys and protocols. In this paper, initial discussions are done on WSN with a detailed overview of sensor, and reviews are made on providing security of wireless sensor network. The proposed novel idea is used in aggregating data during exchanging of messages and to preserve its data privacy and also to overcome problem in network construction (NC) and its security. The NC is done byclustering its topology, and assigning heads to each cluster with huge communication range, also security pattern generation is created for protecting the data information. © Springer India 2016. Source

Discover hidden collaborations