Mantle heat drives hydrothermal fluids responsible for carbonate-hosted base metal deposits: evidence from 3He/4He of ore fluids in the Irish Pb-Zn ore district

There is little consensus on whether carbonate-hosted base metal deposits, such as the world-class Irish Zn+Pb ore field, formed in collisional or extensional tectonic settings. Helium isotopes have been analysed in ore fluids trapped in sulphides samples from the major base metal deposits of the Irish Zn-Pb ore field in order to quantify the involvement of mantle-derived volatiles, that require melting to be realised, as well as test prevailing models for the genesis of the ore fields. 3He/4He ratios range up to 0.2 Ra, indicating that a small but clear mantle helium contribution is present in the mineralising fluids trapped in galena and marcasite. Sulfides from ore deposits with the highest fluid inclusion temperatures (~200°C) also have the highest 3He/4He (> 0.15 Ra). Similar 3He/4He are recorded in fluids from modern continental regions that are undergoing active extension. By analogy we consider that the hydrothermal fluids responsible for the carbonate-hosted Irish base metal mineralization circulated in thinned continental crust, undergoing extension, and demonstrates that enhanced mantle heat flow is ultimately responsible for driving fluid convection

Helium and argon isotope geochemistry of alkaline intrusion-associated gold and copper deposits along the Red River-Jinshajiang fault belt, SW China

The Red River-Jinshajiang strike-slip fault zone on the eastern margin of the Tibetan plateau was originally produced by the India-Eurasia collision ∼60-70 Myr ago. Numerous post-collisional, mantle-derived alkaline igneous rocks, with ages of ∼40-30 Ma, have been intruded along this fault zone. In recent years, several copper and gold deposits associated with the alkaline intrusions of this region were discovered, such as the Yao'an and Beiya gold deposits and the Yulong and Machangqing copper deposits studied in this paper. The mineralised intrusions are felsic, with SiO 2 ranging from 61.4 to 67.7 wt.%, K 2O+Na 2O from 8.1 to 11.5 wt.% and K 2O/Na 2O>1. The deposits are located at both the exo- and endo-contact zones of the intrusions. The mineral deposits are of hydrothermal origin, with the ore-forming temperatures mainly in the range 150-450 °C. This paper presents He and Ar isotope analyses of these four deposits. The concentrations of 4He trapped in fluid inclusions of pyrites from the ores are (0.7-54.1)× 10 -6 cm 3 STP g -1, and those of 40Ar are (0.6-7.3)×10 -6 cm 3 STP g -1, 3He/ 4He ratios are 0.3-2.5 Ra (Ra represents the 3He/ 4He ratio of air, 1.39×10 -6), 40Ar/ 36Ar ratios are 316-1736, and 3He/ 36Ar ratios are 0.2-11.2× 10 -3. Generally, the 3He/ 4He, 40Ar/ 36Ar and 3He/ 36 Ar ratios for the gold deposits are higher than those for the copper deposits. We suggest that the ore-forming fluids of both gold and copper deposits were differentiated from the mantle-derived alkaline magmas, but were diluted by modified air-saturated water (MASW) that experienced intensive interaction with crustal rocks. However, the magmatic fluids responsible for the gold deposits were less extensively diluted by MASW, resulting in higher 3He/ 4He, 40Ar/ 36Ar and 3He/ 36Ar ratios than the copper deposits. © 2003 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

Mantle-derived gaseous components in ore-forming fluids of the Xiangshan uranium deposit, Jiangxi province, China: Evidence from He, Ar and C isotopes

The Xiangshan U deposit, the largest hydrothermal U deposit in China, is hosted in late Jurassic felsic volcanic rocks although the U mineralization post dates the volcanics by at least 20 Ma. The mineralization coincides with intrusion of local mantle-derived mafic dykes formed during Cretaceous crustal extension in South China. Ore-forming fluids are rich in CO 2, and U in the fluid is thought to have been dissolved in the form of UO 2 (CO 3) 2 2- and UO 2 (CO 3) 3 4- complexes. This paper provides He and Ar isotope data of fluid inclusions in pyrites and C isotope data of calcites associated with U mineralization (pitchblende) in the Xiangshan U deposit. He isotopic compositions range between 0.1 and 2.0Ra (where Ra is the 3He/ 4He ratio of air = 1.39 × 10 - 6) and correlates with 40Ar/ 36Ar; although there is potential for significant 3He production via 6Li(n,α) 3H(β) 3He reactions in a U deposit (due to abundant neutrons), nucleogenic production cannot account for either the 3He concentration in these fluids, nor the correlations between He and Ar isotopic compositions. It is more likely that the high 3He/ 4He ratios represent trapped mantle-derived gases. A mantle origin for the volatiles of Xiangshan is consistent with the δ 13C values of calcites, which vary from - 3.5‰ to - 7.7‰, overlapping the range of mantle CO 2. The He, Ar and CO 2 characteristics of the ore-forming fluids responsible for the deposit are consistent with mixing between 3He- and CO 2-rich mantle-derived fluids and CO 2-poor meteoric fluids. These fluids were likely produced during Cretaceous extension and dyke intrusion which permitted mantle-derived CO 2 to migrate upward and remobilize U from the acid volcanic source rocks, resulting in the formation of the U deposit. Subsequent decay of U within the fluid inclusions has reduced the 3He/ 4He ratio, and variations in U/ 3He result in the range in 3He/ 4He observed with U/ 3He ratios in the range 5-17 × 10 3 likely corresponding to U concentrations in the fluids < 0.2 ppm. © 2008 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

Practice-based learning: Multiple dimensions and the importance of others

Learning to become a professional, autonomous clinician requires the acquisition of an extensive set of knowledge, skills and behaviours. Regular immersion in the complex and diverse world of professional practice is a crucial aspect of the learning journey. In this chapter we argue that for practice-based learning to be both effective and meaningful it must include an appreciation of the multidimensional nature of healthcare. For graduates to be work-ready, they should previously have encountered three key dimensions of practice. First, as students they should have achieved competence and confidence in working and learning with a range of others. This starts with fellow students, gaining teamwork and collaboration skills

Teaching methods in Hawler College of Medicine in Iraq: A qualitative assessment from teachers' perspectives

<p>Abstract</p> <p>Background</p> <p>Medical education in Iraq is poorly assessed and there is a general lack of documented knowledge about the challenges facing this field and the needs for its development. This study aimed to assess the existing teaching methods in the Hawler College of Medicine, Iraq from teaching staff perspectives and assess the knowledge of the teaching staff about student-centred learning.</p> <p>Methods</p> <p>A qualitative study based on a self-administered questionnaire survey of a purposive sample of 83 teaching staff in Hawler Medical University was conducted. The questionnaire addressed the participants’ view on the positive aspects and problems of the current teaching methods and priorities to change it. The qualitative data analysis comprised thematic analysis.</p> <p>Results</p> <p>The study revealed significant problems facing the existing teaching methods including having large number of students in the lecture hall (45.0 %), having focus on teacher-centred teaching (45.0 %) and lack of infrastructures and facilities suitable for proper teaching (26.7 %). The priorities for improving the quality of teaching methods included adoption of small group teaching strategy in all study years (34.6 %), improving the infrastructure and facilities for teaching in the college (34.6 %) and provision of continuous academic development programs for the teaching staff (24.3 %).</p> <p>Conclusions</p> <p>The existing medical education system face significant problems and it needs important and comprehensive improvements in different areas. There is a need for further research in this field to explore the identified problems in a more in-depth manner in order to better understand of the problems and needs of this important area of education.</p

Helium solubility in olivine and implications for high ³He/⁴He in ocean island basalts

High 3He/4He ratios found in ocean island basalts are the main evidence for the existence of an undegassed mantle reservoir1, 2, 3. However, models of helium isotope evolution depend critically on the chemical behaviour of helium during mantle melting. It is generally assumed that helium is strongly enriched in mantle melts relative to uranium and thorium, yet estimates of helium partitioning in mantle minerals have produced conflicting results4, 5, 6. Here we present experimental measurements of helium solubility in olivine at atmospheric pressure. Natural and synthetic olivines were equilibrated with a 50% helium atmosphere and analysed by crushing in vacuo followed by melting, and yield a minimum olivine–melt partition coefficient of 0.0025 0.0005 (s.d.) and a maximum of 0.0060 0.0007 (s.d.). The results indicate that helium might be more compatible than uranium and thorium during mantle melting and that high 3He/4He ratios can be preserved in depleted residues of melting. A depleted source for high 3He/4He ocean island basalts would resolve the apparent discrepancy7 in the relative helium concentrations of ocean island and mid-ocean-ridge basalts

Development and psychometric testing of the Visual Analogue Scale for Irritable Bowel Syndrome (VAS-IBS)

Background: The aim of this study was to develop and psychometrically test a short, patient-reported questionnaire to be used in clinical practice for patients with Irritable Bowel Syndrome (IBS). The Visual Analogue Scale for Irritable Bowel Syndrome (VAS-IBS) questionnaire was designed to measure the treatment response of symptoms and well-being in patients suffering from IBS. Methods: The VAS-IBS was psychometrically tested for content and criterion validity, scale acceptability, item-reduction, internal reliability consistency, simplicity, and speed. Two samples were used. One expert panel (five physicians and four registered nurses), who gave their opinion on the content validity, and one of 71 patients with IBS (mean age 38 years SD + 13, range 19-65), who completed the VAS-IBS, as well as the Gastrointestinal Symptom Rating Scale and the Psychological General Well-Being Index for criterion validity. Results: The items in the VAS-IBS capture the main physical concerns women with IBS might present and the psychometric testing confirmed that the VAS-IBS is an acceptable homogeneous patient-reported questionnaire indicated by Cronbach's alpha internal consistency reliability coefficient, with a value of 0.85. All correlations to test the criterion validity performed by using Pearson's correlation test, were statistically significant (p &lt; 0.0001) and in the expected directions. The VAS-IBS is easy to complete and unproblematic to calculate. Conclusion: The VAS-IBS appears to be reliable and user-friendly, for patients as well as for health professionals. The final version of the VAS-IBS including nine items needs to be further tested in clinical practice cross-culturally in women as well as in men