Magmatic and hydrothermal behavior of uranium in syntectonic leucogranites: The uranium mineralization associated with the Hercynian Guérande granite (Armorican Massif, France)

Most of the hydrothermal uranium (U) deposits from the European Hercynian belt (EHB) are spatially associated with Carboniferous peraluminous leucogranites. In the southern part of the Armorican Massif (French part of the EHB), the Guérande peraluminous leucogranite was emplaced in an extensional deformation zone at ca. 310 Ma and is spatially associated with several U deposits and occurrences. The apical zone of the intrusion is structurally located below the Pen Ar Ran U deposit, a perigranitic vein-type deposit where mineralization occurs at the contact between black shales and Ordovician acid metavolcanics. In the Métairie-Neuve intragranitic deposit, uranium oxide-quartz veins crosscut the granite and a metasedimentary enclave. Airborne radiometric data and published trace element analyses on the Guérande leucogranite suggest significant uranium leaching at the apical zone of the intrusion. The primary U enrichment in the apical zone of the granite likely occurred during both fractional crystallization and the interaction with magmatic fluids. The low Th/U values (18Owhole rock = 9.7–11.6‰ for deformed samples and δ18Owhole rock = 12.2–13.6‰ for other samples) indicate that the deformed facies of the apical zone underwent sub-solidus alteration at depth with oxidizing meteoric fluids. Fluid inclusion analyses on a quartz comb from a uranium oxide-quartz vein of the Pen Ar Ran deposit show evidence of low-salinity fluids (1–6 wt.% NaCl eq.), in good agreement with the contribution of meteoric fluids. Fluid trapping temperatures in the range of 250–350 °C suggest an elevated geothermal gradient, probably related to regional extension and the occurrence of magmatic activity in the environment close to the deposit at the time of its formation. U-Pb dating on uranium oxides from the Pen Ar Ran and Métairie-Neuve deposits reveals three different mineralizing events. The first event at 296.6 ± 2.6 Ma (Pen Ar Ran) is sub-synchronous with hydrothermal circulations and the emplacement of late leucogranitic dykes in the Guérande leucogranite. The two last mineralizing events occur at 286.6 ± 1.0 Ma (Métairie-Neuve) and 274.6 ± 0.9 Ma (Pen Ar Ran), respectively. Backscattered uranium oxide imaging combined with major elements and REE geochemistry suggest similar conditions of mineralization during the two Pen Ar Ran mineralizing events at ca. 300 Ma and ca. 275 Ma, arguing for different hydrothermal circulation phases in the granite and deposits. Apatite fission track dating reveals that the Guérande granite was still at depth and above 120 °C when these mineralizing events occurred, in agreement with the results obtained on fluid inclusions at Pen Ar Ran. Based on this comprehensive data set, we propose that the Guérande leucogranite is the main source for uranium in the Pen Ar Ran and Métairie-Neuve deposits. Sub-solidus alteration via surface-derived low-salinity oxidizing fluids likely promoted uranium leaching from magmatic uranium oxides within the leucogranite. The leached out uranium may then have been precipitated in the reducing environment represented by the surrounding black shales or graphitic quartzites. As similar mineralizing events occurred subsequently until ca. 275 Ma, meteoric oxidizing fluids likely percolated during the time when the Guérande leucogranite was still at depth. The age of the U mineralizing events in the Guérande region (300–275 Ma) is consistent with that obtained on other U deposits in the EHB and could suggest a similar mineralization condition, with long-term upper to middle crustal infiltration of meteoric fluids likely to have mobilized U from fertile peraluminous leucogranites during the Late Carboniferous to Permian crustal extension events

Platinum group element mineralization at Musongati (Burundi) : concentration and Pd-Rh distribution in pentlandite

The mafic-ultramafic intrusions of the Karagwe-Ankole belt in Burundi are considered as a new potential source for platinum group elements (PGE). The intrusions have mainly been studied for their PGE potential with regard to PGE concentration, but the mineralogical distribution of PGE has not been examined to the same level. This study focuses on the Pd and Rh distribution in pentlandite of ultramafic rocks of the Musongati layered intrusion. The results are based on whole rock and pentlandite analyses which were incorporated into a mass balance. Palladium proportions in pentlandite vary between 4 and 69%. Rhodium is present in proportions ranging from 1-39% in pentlandite. Other PGE distributions could not be determined in pentlandite due to concentrations below detection limits. The results from this study demonstrate that Pd and Rh are hosted by sulfides since sulfur saturation of the magma occurred early on, perhaps before or simultaneously with the precipitation of silicate minerals. Based on these findings, a preliminary model for the mineralization of PGE in the Musongati intrusion is proposed

Magmatic Cu-Ni-PGE-Au sulfide mineralisation in alkaline igneous systems: An example from the Sron Garbh intrusion, Tyndrum, Scotland

Magmatic sulfide deposits typically occur in ultramafic-mafic systems, however, mineralisation can occur in more intermediate and alkaline magmas. Sron Garbh is an appinite-diorite intrusion emplaced into Dalradian metasediments in the Tyndrum area of Scotland that hosts magmatic Cu-Ni-PGE-Au sulfide mineralisation in the appinitic portion. It is thus an example of magmatic sulfide mineralisation hosted by alkaline rocks, and is the most significantly mineralised appinitic intrusion known in the British Isles. The intrusion is irregularly shaped, with an appinite rim, comprising amphibole cumulates classed as vogesites. The central portion of the intrusion is comprised of unmineralised, but pyrite-bearing, diorites. Both appinites and diorites have similar trace element geochemistry that suggests the diorite is a more fractionated differentiate of the appinite from a common source that can be classed with the high Ba-Sr intrusions of the Scottish Caledonides. Mineralisation is present as a disseminated, primary chalcopyrite-pyrite-PGM assemblage and a blebby, pyrite-chalcopyrite assemblage with significant Co-As-rich pyrite. Both assemblages contain minor millerite and Ni-Co-As-sulfides. The mineralisation is Cu-, PPGE-, and Au-rich and IPGE-poor and the platinum group mineral assemblage is overwhelmingly dominated by Pd minerals; however, the bulk rock Pt/Pd ratio is around 0.8. Laser ablation analysis of the sulfides reveals that pyrite and the Ni-Co-sulfides are the primary host for Pt, which is present in solid solution in concentrations of up to 22 ppm in pyrite. Good correlations between all base and precious metals indicate very little hydrothermal remobilisation of metals despite some evidence of secondary pyrite and PGM. Sulfur isotope data indicate some crustal S in the magmatic sulfide assemblages. The source of this is unlikely to have been the local quartzites, but S-rich Dalradian sediments present at depth. The generation of magmatic Cu-Ni-PGE-Au mineralisation at Sron Garbh can be attributed to post-collisional slab drop off that allowed hydrous, low-degree partial melting to take place that produced a Cu-PPGE-Au-enriched melt, which ascended through the crust, assimilating crustal S from the Dalradian sediments. The presence of a number of PGE-enriched sulfide occurrences in appinitic intrusions across the Scottish Caledonides indicates that the region contains certain features that make it more prospective than other alkaline provinces worldwide, which may be linked the post-Caledonian slab drop off event. We propose that the incongruent melting of pre-existing magmatic sulfides or ‘refertilised’ mantle in low-degree partial melts can produce characteristically fractionated, Cu-PPGE-Au-semi metal bearing, hydrous, alkali melts, which, if they undergo sulfide saturation, have the potential to produce alkaline-hosted magmatic sulfide deposits

Intrusion Detection System using Bayesian Network Modeling

Computer Network Security has become a critical and important issue due to ever increasing cyber-crimes. Cybercrimes are spanning from simple piracy crimes to information theft in international terrorism. Defence security agencies and other militarily related organizations are highly concerned about the confidentiality and access control of the stored data. Therefore, it is really important to investigate on Intrusion Detection System (IDS) to detect and prevent cybercrimes to protect these systems. This research proposes a novel distributed IDS to detect and prevent attacks such as denial service, probes, user to root and remote to user attacks. In this work, we propose an IDS based on Bayesian network classification modelling technique. Bayesian networks are popular for adaptive learning, modelling diversity network traffic data for meaningful classification details. The proposed model has an anomaly based IDS with an adaptive learning process. Therefore, Bayesian networks have been applied to build a robust and accurate IDS. The proposed IDS has been evaluated against the KDD DAPRA dataset which was designed for network IDS evaluation. The research methodology consists of four different Bayesian networks as classification models, where each of these classifier models are interconnected and communicated to predict on incoming network traffic data. Each designed Bayesian network model is capable of detecting a major category of attack such as denial of service (DoS). However, all four Bayesian networks work together to pass the information of the classification model to calibrate the IDS system. The proposed IDS shows the ability of detecting novel attacks by continuing learning with different datasets. The testing dataset constructed by sampling the original KDD dataset to contain balance number of attacks and normal connections. The experiments show that the proposed system is effective in detecting attacks in the test dataset and is highly accurate in detecting all major attacks recorded in DARPA dataset. The proposed IDS consists with a promising approach for anomaly based intrusion detection in distributed systems. Furthermore, the practical implementation of the proposed IDS system can be utilized to train and detect attacks in live network traffi

The application of S isotopes and S/Se ratios in determining ore-forming processes of magmatic Ni–Cu–PGE sulfide deposits: a cautionary case study from the northern Bushveld Complex

The application of S/Se ratios and S isotopes in the study of magmatic Ni–Cu–PGE sulfide deposits has long been used to trace the source of S and to constrain the role of crustal contamination in triggering sulfide saturation. However, both S/Se ratios and S isotopes are subject to syn- and post-magmatic processes that may alter their initial signatures. We present in situ mineral δ34S signatures and S/Se ratios combined with bulk S/Se ratios to investigate and assess their utility in constraining ore-forming processes and the source of S within magmatic sulfide deposits. Magmatic Ni–Cu–PGE sulfide mineralization in the Grasvally Norite–Pyroxenite–Anorthosite (GNPA) member, northern Bushveld Complex was used as a case study based on well-defined constraints of sulfide paragenesis and local S isotope signatures. A crustal δ34S component is evident in the most primary sulfide assemblage regardless of footwall lithology, and is inferred that the parental magma(s) of the GNPA member was crustally contaminated and sulfide saturated at the time of emplacement. However, S/Se ratios of both the primary and in particular secondary sulfide assemblages record values within or below the mantle range, rather than high crustal S/Se ratios. In addition, there is a wide range of S/Se ratio for each sulfide mineral within individual assemblages that is not necessarily consistent with the bulk ratio. The initial crustal S/Se ratio is interpreted to have been significantly modified by syn-magmatic lowering of S/Se ratio by sulfide dissolution, and post-magmatic lowering of the S/Se ratio from hydrothermal S-loss, which also increases the PGE tenor of the sulfides. Trace element signatures and variations in Th/Yb and Nb/Th ratios support both an early pre-emplacement contamination event as seen by the S isotopes and S/Se ratios, but also a second contamination event resulting from the interaction of the GNPA magma with the local footwall country rocks at the time of emplacement; though this did not add any additional S. We are able to present an integrated emplacement and contamination model for the northern limb of the Bushveld Complex. Although the multitude of processes that affect variations in the δ34S signature and in particular S/Se ratio may be problematic in interpreting ore genesis, they can reveal a wealth of additional detail on a number of processes involved in the genetic history of a Ni–Cu–PGE deposit in addition to crustal contamination. However, a prerequisite for being able to do this is to utilize other independent petrological and mineralogical techniques that provide constraints on both the timing and effect of various ore-forming and modifying processes. Utilizing both bulk and in situ methods in concert to determine the S/Se ratio allows for the assessment of multiple sulfide populations, the partitioning behaviour of Se during sulfide liquid fractionation and also the effects of low temperature fluid alteration. In comparison, S isotopes are relatively more robust and represent a more reliable indicator of the role of crustal S contamination. The addition of trace element data to the above makes for an incredibly powerful approach in assessing the role of crustal contamination in magmatic sulfide systems

Hierarchical Design Based Intrusion Detection System For Wireless Ad hoc Network

In recent years, wireless ad hoc sensor network becomes popular both in civil and military jobs. However, security is one of the significant challenges for sensor network because of their deployment in open and unprotected environment. As cryptographic mechanism is not enough to protect sensor network from external attacks, intrusion detection system needs to be introduced. Though intrusion prevention mechanism is one of the major and efficient methods against attacks, but there might be some attacks for which prevention method is not known. Besides preventing the system from some known attacks, intrusion detection system gather necessary information related to attack technique and help in the development of intrusion prevention system. In addition to reviewing the present attacks available in wireless sensor network this paper examines the current efforts to intrusion detection system against wireless sensor network. In this paper we propose a hierarchical architectural design based intrusion detection system that fits the current demands and restrictions of wireless ad hoc sensor network. In this proposed intrusion detection system architecture we followed clustering mechanism to build a four level hierarchical network which enhances network scalability to large geographical area and use both anomaly and misuse detection techniques for intrusion detection. We introduce policy based detection mechanism as well as intrusion response together with GSM cell concept for intrusion detection architecture.Comment: 16 pages, International Journal of Network Security & Its Applications (IJNSA), Vol.2, No.3, July 2010. arXiv admin note: text overlap with arXiv:1111.1933 by other author