Exotic accessory minerals in layered chromities of the Campo Formoso complex (Brazil)

The Campo Formoso stratiform intrusive complex, in Bahia State, Brazil, considered to be of Paleoproterozoic age, consists of a tabular body of ultramafic rocks about 40 km long and 100-1100 m wide. Thick horizons of chromitite are exploited and the deposits are the richest in Brazil. The complex was intruded by the Campo Formoso calc-alkaline batholith, emplaced by the result of the Transamazonian collision-related orogeny. The peridotite was firstly thoroughly serpentinized, then affected by a renewed cycle of hydrothermal alteration as the batholith cooled, leading in the roof zone to emerald mineralization around roof pendants. An even later influx of fluid led to the formation of talc, silica and carbonates, such that the ultramafic rocks were locally converted to listwanite. The chromitite sequences are highly unusual in containing rather exotic minerals, such as monazite-(La), monazite-(Ce), apatite, galena, bismuthinite, antimony, and three unknown minerals of stoichiometry PbSb2, Pb6Sb and PbSb4, all associated with the clinochlore. The latter phases may have formed during hydrothermal activity in the system Pb-Sb. The presence of these exotic minerals in chromitite, which makes this occurrence unique in the world, strongly support the hypothesis that the La, Ce, P, Pb, Bi and Sb were metasomatically added to the Campo Formoso chromitite horizons by hydrothermal fluids emanating from the nearby Campo Formoso calc-alkaline batholith as it cooled

The Stillwater Complex chromitites : the response of chromite crystal chemistry to magma injection

Nineteen chromite crystals from the A, B, E, G, H, J and K chromitite layers of the Peridotite Zone of the Stillwater Complex (Montana, USA) have been studied by means of X-ray single crystal diffraction and microprobe analyses. The results show that samples from the basal A layer are quite different from the others showing very high oxygen positional parameter u (0.2633-0.2635) and Ti- contents (0.059-0.067apfu). Mg# values are within the range 0.21-0.23 while for the other chromites it is in the range 0.45-0.47. Moreover, for the other samples, according to the structural parameters, two groups have been identified. The first one comprises samples of layers B, E and G, the second includes H, J and K layer samples. It is supposed that high Fe2+ and Ti contents of A layer samples are due to the post-crystallization reaction with interstitial liquid. This fact allowed a very slow cooling rate as evidenced by the high u values. The fractionation of evolved magma from within the intrusion and pulse of a new magma bringing more chromium into the chamber lead to Cr- and Fe3+ -rich compositions and consequently to the increase of the cell edges. The decrease of u values seems to be related to the Cr+Fe3+ and/or Al contents

Exotic accessory minerals in layered chromitites of the Campo Formoso complex (Brazil)

The Campo Formoso stratiform intrusive complex, in Bahia State, Brazil, considered to be of Paleoproterozoic age, consists of a tabular body of ultramafic rocks about 40 km long and 100-1100 m wide. Thick horizons of chromitite are exploited and the deposits are the richest in Brazil. The complex was intruded by the Campo Formoso calc-alkaline batholith, emplaced by the result of the Transamazonian collision-related orogeny. The peridotite was firstly thoroughly serpentinized, then affected by a renewed cycle of hydrothermal alteration as the batholith cooled, leading in the roof zone to emerald mineralization around roof pendants. An even later influx of fluid led to the formation of talc, silica and carbonates, such that the ultramafic rocks were locally converted to listwanite. The chromitite sequences are highly unusual in containing rather exotic minerals, such as monazite-(La), monazite-(Ce), apatite, galena, bismuthinite, antimony, and three unknown minerals of stoichiometry PbSb2, Pb Sb and PbSb4, all associated with the clinochlore. The latter phases may have formed during hydrothermal activity in the system Pb-Sb. The presence of these exotic minerals in chromitite, which makes this occurrence unique in the world, strongly support the hypothesis that the La, Ce, P, Pb, Bi and Sb were metasomatically added to the Campo Formoso chromitite horizons by hydrothermal fluids emanating from the nearby Campo Formoso calc-alkaline batholith as it cooled

Thalhammerite, Pd9Ag2Bi2S4, a New Mineral from the Talnakh and Oktyabrsk Deposits, Noril'sk Region, Russia

This is an Open Access publicatiomThe file attached is the Published/publisher’s pdf version of the article

Chromite and platinum group elements mineralization in the Santa Elena Ultramafic Nappe (Costa Rica): geodynamic implications

Chromitites associated with strongly altered peridotite from six distinct localities in the Santa Elena ultramafic nappe (Costa Rica) have been investigated for the first time. Santa Elena chromitites commonly display a compositional variation from extremely chromiferous (Cr/(Cr+Al)=0.81) to intermediate and aluminous (Cr/(Cr+Al)=0.54). This composition varies along a continuous trend, corresponding to calculated parental liquids which may have been derived from the differentiation of a single batch of boninitic magma with Cr-rich and (Al, Ti)-poor initial composition. Fractional precipitation of chromite probably occurred during differentiation of the boninitic melt and progressive metasomatic reaction with mantle peridotite. The distribution of platinum group elements (PGE) displays the high (Os+Ir+Ru)/(Rh+Pt+Pd) ratio typical of ophiolitic chromitites and, consistently, the platinum group minerals (PGM) encountered are mainly Ru-Os-Ir sulfides and arsenides. Textural relations of most of the platinum group elements suggest crystallization at magmatic temperatures, possibly under relatively high sulfur fugacity as indicated by the apparent lack of primary Os-Ir-Ru alloys. The chemical and mineralogical characteristics of chromitites from the Santa Elena ultramafic nappe have a strong affinity to podiform chromitites in the mantle section of supra-subduction-zone ophiolites. Calculated parental melts of the chromitites are consistent with the differentiation of arc-related magmas, and do not support the oceanic spreading center geodynamic setting previously proposed by some authors

1-(4-Bromo­phen­yl)-2-(phenyl­sulfon­yl)ethanone

The overall conformation of the title mol­ecule, C14H11BrO3S, is L-shaped, as seen in the value of the dihedral angle formed between the terminal benzene rings of 75.44 (13)°. The presence of C—H⋯O inter­actions leads to the formation of linear supra­molecular chains along the a-axis direction in the crystal structure. These are connected into supra­molecular arrays in the ab plane via C—H⋯π contacts

Labile plasma iron and echocardiographic parameters are associated to cardiac events in beta-thalassemic patients

Background and aim: Notwithstanding the improvement in therapies, patients affected by thalassemia major (TM) and intermedia (TI) are still at high risk of cardiac complications. This study aimed at evaluating the incidence and predictive factors for developing cardiac events in adult β-TM and TI patients. Population andmethods: Data on diagnosis and clinical historywere collected retrospectively; prospective data on new-onset cardiac failure and arrhythmias, echocardiographic parameters, biochemical variables including non-transferrin-bound iron (NTBI) and labile plasma iron (LPI), magnetic resonance imaging (MRI) T2* measurement of hepatic and cardiac iron deposits, and iron chelation therapy were recorded during a 6 year follow-up. Results: Thirty-seven patients, 29 TM and 8 TI, were included. At baseline, 8 TM patients and 1 TI patient had previously experienced a cardiac event (mainly heart failure). All patients were on chelation therapy and only 3 TM patients had mild-to-severe cardiac siderosis. During follow-up, 11 patients (29.7%) experienced a new cardiac event. The occurrence of cardiac events was correlated to high LPI levels (OR 12.0, 95% CI 1.56-92.3, p 0.017), low mean pre-transfusion hemoglobin (OR 0.21, 95% C.I. 0.051-0.761, p 0.21), and echocardiographic parameters suggestive of myocardial hypertrophy. Multivariate analysis disclosed high LPI and left ventricle mass index (LVMI) as independent variables significantly associated with cardiac events. Cardiac iron deposits measured by MRI T2* failed to predict cardiac events. Conclusion: LPI, Hb levels, and echocardiographic parameters assessing cardiac remodeling are associated to cardiac events in adult TM and TI patients. LPI might represent both a prognostic marker and a potential target for novel treatment strategies. Further studies are warranted to confirm our findings on larger population

Atrial Fibrillation and Other Cardiovascular Factors and the Risk of Dementia: An Italian Case–Control Study

: Dementia is a major neurologic syndrome characterized by severe cognitive decline, and it has a detrimental impact on overall physical health, leading to conditions such as frailty, changes in gait, and fall risk. Depending on whether symptoms occur before or after the age of 65, it can be classified as early-onset (EOD) or late-onset (LOD) dementia. The present study is aimed at investigating the role of cardiovascular factors on EOD and LOD risk in an Italian population. Using a case-control study design, EOD and LOD cases were recruited at the Modena Cognitive Neurology Centers in 2016-2019. Controls were recruited among caregivers of all the dementia cases. Information about their demographics, lifestyles, and medical history were collected through a tailored questionnaire. We used the odds ratio (OR) and 95% confidence interval (CI) to estimate the EOD and LOD risk associated with the investigated factors after adjusting for potential confounders. Of the final 146 participants, 58 were diagnosed with EOD, 34 with LOD, and 54 were controls. According to their medical history, atrial fibrillation was associated with increased disease risk (ORs 1.90; 95% CI 0.32-11.28, and 3.64; 95% CI 0.32-41.39 for EOD and LOD, respectively). Dyslipidemia and diabetes showed a positive association with EOD, while the association was negative for LOD. We could not evaluate the association between myocardial infarction and EOD, while increased risk was observed for LOD. No clear association emerged for carotid artery stenosis or valvular heart disease. In this study, despite the limited number of exposed subjects and the high imprecision of the estimates, we found positive associations between cardiovascular disease, particularly dyslipidemia, diabetes, and atrial fibrillation, and EOD