Implications of the dominant LP–HT deformation in the Guanhães Block for the Araçuaí West-Congo Orogen evolution

The Araçuaí-West Congo Orogen is the result of convergence between the São Francisco and Congo cratons during the assembly of West Gondwana. Within this orogen, the Araçuaí Belt in SE Brazil reflects the western external domain. The Araçuaí Belt is characterized by major east-dipping structures and high- to medium pressure metamorphic rocks developed during crustal thickening at ca. 585–560 Ma and are juxtaposed along crustal-scale structures to the crystalline core of the orogen. The Guanhães Block in the southern Araçuaí Belt is characterized by higher metamorphic grade and dominantly shallowly west-dipping structures compared to the neighboring tectonic domains. While several studies have focused on the evolution of the axial crystalline core of the Araçuaí orogen and on the early collisional stages in the Araçuaí Belt, little attention has been given to the structural and metamorphic history of the poorly studied Guanhães Block. The supracrustal rocks in the central Guanhães Block record two tectono-metamorphic stages: D2/M2 and D3 /M3, with potential D1/M1 relicts rarely preserved within D2/M2 low-strain domains. The D2/M2 overprinting stage is associated with the development of a dominant, shallow axial planar foliation (S2) of isoclinal F2 folds under low-pressure and high-temperature (LP–HT) conditions (ca. 6 kbar and 750 °C). During this D2/M2 stage continuous segregation of syn-kinematic partial melting and generation of granitoid rocks occurred. The 530 Ma, syn- D2/M2 granitoid has negative εHf(i) at ca. −32 which indicates the source of magma from melting of older, isotopically evolved, Archaean or Paleoproterozoic crust. U–Pb geochronology on monazite, titanite and hydrothermal zircon constrain the retrograde D3/M3 event at ca. 510 Ma. The Guanhães Block uniquely records dominant deformation under LP–HT metamorphic conditions during the late-orogenic stages and its evolution could have important tectonic implications for the concurrent models suggested for the late Neoproterozoic Araçuaí-West Congo Orogen

Hydrothermal fluid processes and evolution of the giant serra norte jaspilite-hosted iron ore deposits, carajás mineral Province, Brazil.

The Serra Norte Carajás banded iron-formation (BIF)-hosted iron ore deposits are located in the Carajás mineral province. The deposits are hosted in the ca. 2.7 Ga Grão Pará Group, a metamorphosed volcanic-sedimentary sequence where jaspilites are under- and overlain by basalts, both at greenschist facies conditions. They represent one of the largest high-grade (>60 wt % Fe) BIF iron ore deposits and resources in the world, with hypogene iron mineralization considered to be Paleoproterozoic. Four main open pits have, to date, produced about 1.2 billion metric tons (Bt) of high-grade iron ore with additional resources of 10 Bt. Ore types at the Serra Norte deposits include soft and hard ore; the latter consists of banded, massive and/or brecciated ores and is mainly localized along the contact with the surrounding hydrothermally altered basalts. Distinct hydrothermal alteration zones consist of veins and breccias that surround the hard ores, including: (1) an early alteration zone (distal portion of orebodies), characterized by recrystallization of jasper, formation of magnetite (± martite), and the local introduction of quartz and carbonate-sulfide (±quartz) veins; (2) intermediate alteration, synchronous with the main iron ore-forming event, which is accompanied by widespread development of martite, quartz-hematite and hematite-quartz veins, and dissolution of carbonate; and (3) proximal alteration zone having various types of hard and hard-porous hematite ores containing microplaty, anhedral, euhedral, and tabular hematite species. Locally, high-grade breccia ores contain dolomite and kutnahorite matrices indicating carbonate introduction. High-grade ore zones contain quartz ± carbonatehematite veins and breccias. Combined microthermometry, iron chromatography, and in situ laser ablation ICP-MS analyses on fluid inclusion assemblages from five vein types reveal that (1) early alteration vein-breccia quartz-carbonate contains high-salinity (up to 30 equiv wt % NaCl) fluid inclusions, with Ca, besides Na, K, and Mg, which were trapped at temperatures of 220° to 320°C. The quartz-hosted fluid inclusions have a wide range of Cl/Br ratios, presence of Li, base metals Cu-Pb-Zn, and Fe; (2) intermediate alteration vein quartz contains both low-salinity (Na-Fe-Mg-rich) and high-salinity (Ca-Mg-Fe-rich) fluid inclusions, with trapping temperatures of 210° to 290°C; (3) advanced alteration vein and breccia quartz-carbonate has low- to high-salinity fluid inclusions and trapping temperatures between 240° to 310°C, with the low-salinity inclusions being much more abundant in quartz. There is a gradual dilution of the metals signature in fluid inclusions from early to late- and/or advanced-stage veins and breccias. The large amount of Ca in the fluid inclusions is compatible with extensive exchange of the hydrothermal fluids with the surrounding chloritized-hematitized metabasaltic wall rock. Oxygen isotope analyses on different oxide species reveal that the heaviest δ18OSMOW values, up to 15.2‰, are recorded for jaspilites, followed by magnetite, between -0.4 to +4.3‰, and then by different hematite species such as microplaty, anhedral and tabular, which fall in the range of -9.5 to -2.4‰. These results show a progressive depletion in δ18O values from the earliest introduced hydrothermal oxide magnetite toward the latest tabular hematite. The advanced alteration stage in high-grade ore displays the most depleted 18Ov alues and represents the highest fluid/rock ratio during hydrothermal alteration. This depletion is interpreted to result from the progressive mixture of descending, heated meteoric water with ascending modified magmatic fluids. Sulfides from the distal zone of metabasaltic rocks have δ34S values close to 0‰, consistent with a magmatic origin for the sulfur. Heavier δ34S values, of up to 10.8‰, in vein sulfides hosted in jaspilite, may reflect interaction with meteoric waters or, alternatively, variations in fO2 and pH conditions during evolution of the hydrothermal fluid. Calcite-kutnahorite δ13C and δ18O values from the distal alteration zones show a large δ13C range of -5.5 to -2.4‰ and a relatively narrow δ18O range of 9.3 to 11.7‰. However, dolomite matrix breccias from the advanced hydrothermal zone, i.e., ore, exhibit a wider δ18O range from 15.1 to 21.8‰ and a more restricted δ13C range from -5.0 to -3.9‰. This latter range points to a single carbon source, of possible magmatic nature, whereas the larger δ18O range suggests multiple carbon and oxygen sources. The 87Sr/86Sr ratios for carbonates from the distal and advanced hydrothermal zones range between 0.7116 to 0.7460, suggesting incorporation of strontium from multiple crustal sources, including magmatic-hydrothermal fluids. A dual magmatic-meteoric hydrothermal fluid-flow model is proposed for the hematite ores in which an early, low Cl/Br ratio, saline, ascending modified magmatic fluid, caused widespread oxidation of magnetite to hematite. Progressive influx of light δ18O meteoric water, mixing with the ascending magmatic fluids, is interpreted to have been initiated during the intermediate stage of alteration. The advanced and final hydrothermal stage was dominated by a massive influx of low-salinity meteoric water, which maintained intermediate temperatures of 240° to 310°C, and concomitant formation of the paragenetically latest tabular hematite. The giant Carajás iron deposits are unique in their setting within an Archean granite-greenstone belt and their modified magmatic-meteoric hydrothermal system, compared to the other two end-member BIF iron deposit types, namely the basin-related Hamersley type and the metamorphosed metasedimentary- basin-related Iron-Quadrangle-type. The distinct hydrothermal alteration signature present in both wall-rock basalts and jaspilites, in combination with distinct fluid chemistry signatures, particularly the low δ18O values of paragenetically late oxides indicative of massive influx of meteoric water into the high-grade orebodies, provide distinctive parameters for defining the Carajás end-member type BIF deposit class

Evidences that human disturbance simplify the ant fauna associated a Stachytarpheta glabra Cham. (Verbenaceae) compromising the benefits of ant-plant mutualism

Interaction among species, like ants and plants through extrafloral nectaries (EFNs), are important components of ecological communities’ evolution. However, the effect of human disturbance on such specific interactions and its ecological consequences is poorly understood. This study evaluated the outcomes of mutualism between ants and the EFN-bearing plant Stachytarpheta glabra under anthropogenic disturbance. We compared the arthropod fauna composition between two groups of twenty plant individuals, one in an area disturbed by human activities and one in a preserved area. We also check the plant investment in herbivory defense and the consequential leaf damage by herbivore. Our results indicate that such disturbances cause simplification of the associated fauna and lack of proper ant mutualist. This led to four times more herbivory on plants of disturbed areas, despite the equal amount of EFN and ant visitors and low abundance of herbivores. The high pressure of herbivory may difficult the re-establishment of S. glabra, an important pioneer species in ferruginous fields, therefore it may affect resilience of this fragile ecological community.As interações entre espécies, como por exemplo formigas e plantas através de nectários extraflorais (NEFs), são importantes componentes na evolução das comunidades. Entretanto, pouco é conhecido sobre os efeitos dos impactos antrópicos em interações específicas e suas consequências ecológicas. Este estudo avaliou os resultados do mutualismo entre formigas e NEF em Stachytarpheta glabra em área impactada pela atividade humana. Nós comparamos a composição e estrutura da fauna de artrópodes, em quarenta plantas de dois grupos, um impactado por atividades humanas e o outro preservado. Nós também avaliamos o investimento da planta em defesas contra herbívoros e os danos foliares causados por herbívoros. Nossos resultados indicam que os distúrbios causam a simplificação da fauna associada e a ausência de uma formiga mutualista anti-herbívoros. Isto leva a quatro vezes mais herbivoria nas plantas da área impactada, a despeito da mesma quantidade encontrada para NEF e formigas visitantes. A grande pressão de herbivoria pode dificultar o reestabelecimento de S. glabra, uma espécie pioneira importante nos campos ferruginosos, dessa forma, afetando a resiliência dessa comunidade ecológica ameaçada

Emerging Nanotechnology in Chronic Respiratory Diseases

A large population, including people of all age groups, is suffering from chronic respiratory diseases worldwide. Asthma, chronic obstructive pulmonary disease, occupational lung diseases, cystic fibrosis, etc. are the most common of these diseases and are noncurable with conventional and currently available therapies. Nanotechnology is emerging as a great therapeutic promise in different spheres including drug delivery systems and is becoming the technology of choice nowadays. The administration of drugs via inhalation helps in avoiding the first-pass metabolism by targeted delivery to the affected site. It has been observed that there is a huge diversity in nanotechnology being used in pulmonary diseases, and thus safety assessment is a challenging as well as important task. The present review focuses on some of the major emerging nanotechnologies for chronic pulmonary diseases and includes some of the latest studies in the field of nanomedicines