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Inherited zircons from S-type granites provide exceptionally good insight into the isotopic heterogeneity of their sources. Zircons from four samples (one granite, two granodiorites, one granodioritic enclave) of Pan-African S-type granite of the Cape Granite Suite (c. 540 Ma) have been the subject of a laser LA-ICP-MS zircon U/Pb study to determine emplacement ages and inheritance. Zircons from three of these samples (2 granodiorites and 1 granodioritic enclave) were also analysed for Hf isotopes by LA-MC-ICP-MS. Ages of inherited cores range from 1,200 to 570 Ma and show Hafnium isotope values (ε) for the crystallisation age ( t) of the different cores that range from −14.1 to +9.1. Magmatic zircons and magmatic overgrowth with concordant spot ages between ca. 525 and ca. 555 Ma show a similar range of ε, between −8.6 and +1.5, whilst ε values calculated at 540 Ma (ε) for inherited cores range from −15.2 to +1.7. Thus, our results show that the time evolved ε arrays of the inherited cores overlap closely with the ε range displayed by the magmatic rims at the time of crystallisation of the pluton. These similarities imply a genetic relationship between magmatic and inherited zircons. Within the inherited cores, four main peak ages can be identified. This, coupled with their large Hf isotopic range, emphasises that the source of the granite is highly heterogeneous. The combination of the U/Pb zircon ages ranges and Hf isotope data implies that: (1) The source of S-type granite consists of crustal material recording several regional events between 1,200 and 600 Ma. This material records the recycling of a much older crust derived from depleted mantle between 1.14 and 2.02 Ga. (2) The homogenisation of Hf isotopic variation in the magma acquired through dissolution of the entrained zircon, via mechanical mixing and/or diffusion between within the granite was particularly inefficient. (3) This evidence argues for the assembly of the pluton through many relatively small magma batches that undergo rapid cooling from their intrusion temperature (ca. 850°C) to background magma chamber temperature that is low enough to ensure that much of the magmatic zircon crystallised rapidly (>80% by 700°C). (4) There is no evidence for the addition of mantle-derived material in the genesis of S-type Cape Granite Suite, where the most mafic granodiorites are strongly peraluminous, relatively low in CaO and KO rich. Interpreted more widely, these findings imply that S-type granites inherit their isotopic characteristic from the source. Source heterogeneity transfers to the granite magma via the genesis of discrete magma batches. The information documented from the S-type CGS zircons has been recorded because the individual batches of magma crystallised the bulk of their magmatic zircon prior to mechanical or diffusional magma homogenisation. This is favoured by zirconium saturation in the magma shortly after emplacement, by partial dissolution of the entrained zircon fraction, as well as by the intrusion of volumetrically subordinate magma batches into a relatively cool pluton. Consequently, evidence recorded within inherited cores will most likely be best preserved in S-type granite plutons intruded at shallow depths. Other studies that have documented similar ε arrays in magmatic zircons have interpreted these to reflect mixing between crustal- and mantle-derived magmas. This study indicates that such arrays may be wholly source inherited, reflecting mixing of a range of crustal materials of different ages and original isotopic signatures. [ABSTRACT FROM AUTHOR]

Abstract: In the southern area of the Barberton Mountain Land, TTG magmas were produced during two distinct, major, magmatic events at ca. 3.44 and 3.23Ga. Here, as in many Archaean terranes, tonalite-trondhjemite-granodiorite (TTG) plutons are closely associated with basaltic to komatiitic greenstones, in this case with some metamorphosed to amphibolite facies, suggesting a possible genetic connection between the two rock groups. Previous partial melting experiments on metabasic rocks have shown that tonalitic to trondhjemitic melts can be produced, coexisting with amphibole- and plagioclase-rich restites, at pressures of 0.8–1.5GPa, and garnet- and pyroxene-rich restites at P ≥1.5GPa. The present experiments on a Barberton greenstone amphibolite confirm the higher pressure findings, except that some amphibole was probably still present. In the case of the 3.23Ga plutons, the inferred geotherm is consistent with that obtained from metamorphic assemblages of this age from within the Theespruit Formation of the Onverwacht Group. The commonly scattered major- and trace-element variations in the Barberton TTG suite imply that magmatic crystal fractionation played a subordinate role in producing the geochemical variations of the magmas. The different TTG plutons probably represent separate magma batches, and the scattered trends within the plutons probably reflect heterogeneities within their source-rocks. The ɛNd values suggest that the TTGs were derived from juvenile crustal sources with depleted-mantle signatures. Thus, metabasaltic rocks are the likely sources of the TTG magmas. However, our partial melting experiments on a typical Lower Onverwacht greenstone amphibolite appear to rule out these particular rocks as sources of the local TTG magmas. Instead, it seems likely that possibly more ancient, less potassic, high-grade, metabasic rocks were the sources of the TTG magmas. Trace-element modelling shows that the TTG suite could have been derived through partial melting of primitive basaltic sources, producing plagioclase-free, hornblende-bearing granulitic to eclogitic restites with >30% garnet. Experiments on garnet stability in the near-liquidus mineral assemblage of a typical 3.44Ga Barberton trondhjemite constrain magma generation to a pressure of at least 1.47GPa. This suggests that the Barberton crust was relatively cool and at least 50km thick by 3.44Ga. The same general argument of high-P melting would hold for the ca. 3.2Ga trondhjemites and tonalities, although the minimum P of melting has not been determined for these rocks. In the case of these rocks, believed to have formed in response to a major terrane accretion event, the high-P–moderate-T signature is also indicated by recent metamorphic studies. In contrast, information is scarce on the processes operating during the 3.44Ga magmato-metamorphic event. The P–T conditions during the 3.44Ga event imply an apparent geothermal gradient of <20°C/km. The transport of fertile, hydrated metabasic material to such depths suggests that both the 3.23 and 3.44Ga magmatic events resulted from significant and rapid crustal thickening. This, in turn, suggests that compressional tectonics operated in the Barberton greenstone belt prior to 3.44Ga. [Copyright &y& Elsevier]

Long-term safety is critical for the development and later use of a vaccine to prevent HIV/AIDS. Likewise, the persistence of vaccine-induced antibodies and their impact on HIV testing must be established. IAVI has sponsored several Phase I and IIA HIV vaccine trials enrolling healthy, HIV-seronegative African volunteers. Plasmid DNA and viral vector based vaccines were tested. No vaccine-related serious adverse events were reported. After completion of vaccine trials conducted between 2001-2007, both vaccine and placebo recipients were offered enrolment into an observational long-term follow-up study (LTFU) to monitor potential late health effects and persistence of immune responses. At scheduled 6-monthly clinic visits, a health questionnaire was administered; clinical events were recorded and graded for severity. Blood was drawn for HIV testing and cellular immune assays. 287 volunteers were enrolled; total follow-up after last vaccination was 1463 person years (median: 5.2 years). Ninety-three (93)% of volunteers reported good health at their last LTFU visit. Infectious diseases and injuries accounted for almost 50% of the 175 reported clinical events, of which over 95% were mild or moderate in severity. There were 30 six pregnancies, six incident HIV infections and 14 volunteers reported cases of social harm. Persistence of immune responses was rare. No safety signal was identified. No potentially vaccine-related medical condition, no immune mediated disease, or malignancy was reported. HIV vaccines studied in these trials had a low potential of induction of persisting HIV antibodies.

Background: An understanding of the health of potential volunteers in Africa is essential for the safe and efficient conduct of clinical trials, particularly for trials of preventive technologies such as vaccines that enroll healthy individuals. Clinical safety laboratory values used for screening, enrolment and follow-up of African clinical trial volunteers have largely been based on values derived from industrialized countries in Europe and North America. This report describes baseline morbidity during recruitment for a multi-center, African laboratory reference intervals study., Methods: Asymptomatic persons, aged 18-60 years, were invited to participate in a cross-sectional study at seven sites (Kigali, Rwanda; Masaka and Entebbe, Uganda; Kangemi, Kenyatta National Hospital and Kilifi, Kenya; and Lusaka, Zambia). Gender equivalency was by design. Individuals who were acutely ill, pregnant, menstruating, or had significant clinical findings were not enrolled. Each volunteer provided blood for hematology, immunology, and biochemistry parameters and urine for urinalysis. Enrolled volunteers were excluded if found to be positive for HIV, syphilis or Hepatitis B and C. Laboratory assays were conducted under Good Clinical Laboratory Practices (GCLP)., Results and Conclusions: Of the 2990 volunteers who were screened, 2387 (80%) were enrolled, and 2107 (71%) were included in the analysis (52% men, 48% women). Major reasons for screening out volunteers included abnormal findings on physical examination (228/603, 38%), significant medical history (76, 13%) and inability to complete the informed consent process (73, 13%). Once enrolled, principle reasons for exclusion from analysis included detection of Hepatitis B surface antigen (106/280, 38%) and antibodies against Hepatitis C (95, 34%). This is the first large scale, multi-site study conducted to the standards of GCLP to describe African laboratory reference intervals applicable to potential volunteers in clinical trials. Approximately one-third of all potential volunteers screened were not eligible for analysis; the majority were excluded for medical reasons.