Copepod community along the Mediterranean coast of Morocco (Southwestern Alboran Sea) during spring

Copepod community along the Mediterranean Moroccan coast was investigated, for the first time, during April 2013. Total abundance varied from 53 to 4557 ind. m-3 and high values were found in coastal waters. Oithona nana and Paracalanus parvus dominated in the entire area and species diversity was decreasing from the West to the East. Hierarchical clustering revealed three groups of stations, depending on their geographic position (western, central and eastern areas). Indicator species analysis pointed out that Clausocalanus furcatus and Gaetanus sp. were significantly associated with Group I, Clausocalanus sp., Centropages sp. and Centropages chierchiae with Group II, whereas Temora longicornis was significantly associated with Group III. Detrended Correspondence Analysis based on the species abundance and environmental variables (temperature, salinity, chlorophyll-a), highlighted a more or less similar setting of stations which was related to salinity and temperature. The presence of three anticyclonic gyres at the northern part of the study area is suggested as the major factor acting on the variability of copepod community along the Mediterranean Moroccan coast

Polymetallic Sulfide–Quartz Vein System in the Koudiat Aïcha Massive Sulfide Deposit, Jebilet Massif, Morocco: Microanalytical and Fluid Inclusion Approaches

The Koudiat Aïcha Zn-Cu-Pb deposit (3–Mt ore @ 3 wt.% Zn, 1 wt.% Pb, 0.6 wt.% Cu) in the Jebilet massif (Morocco) comprises stratabound lenticular orebodies and crosscutting sulfide-bearing quartz ± carbonate veins in the lower Carboniferous Sarhlef volcano sedimentary succession. The veins are characterized by abundant pyrrhotite, sphalerite, subordinate chalcopyrite and galena and rare Ag and Au minerals. The stratabound massive sulfide ores are attributed to a “VMS” type, whereas the origin of the sulfide–quartz ± carbonate veins remains poorly understood. New mineralogical and microanalytical data (SEM, EPMA and LA-ICP-MS) combined with fluid inclusion results point to two-stage vein formation. The early stage involved C–H–O–N Variscan metamorphic fluids which percolated through fractures and shear zones and deposited pyrite at >400 °C, followed by the formation of pyrrhotite and sphalerite (300 ± 20 °C) in quartz veins and in banded and breccia ores. The pyrrhotite–sphalerite mineralization was overprinted by aqueous brines (34 to 38 wt% eq. NaCl + CaCl2) that precipitated carbonate and Cu-Pb sulfides (±Ag-Au) at ~180–210 °C through mixing with low-salinity fluids during tectonic reworking of early-formed structures and in late extension fractures. The latter ore fluids were similar to widspread post-Variscan evaporitic brines that circulated in the Central Jebilet. Overlapping or successive pulses of different ore fluids, i.e., metamorphic fluids and basinal brines, led to metal enrichment in the quartz–carbonate veins compared to the massive sulfide ores. These results underscore that even a single deposit may record several distinct mineralizing styles, such that the ultimate metal endowment may be cumulative over multiple stages

Gold remobilisation and formation of high grade ore shoots driven by dissolution-reprecipitation replacement and Ni substitution into auriferous arsenopyrite

Both gold-rich sulphides and ultra-high grade native gold oreshoots are common but poorly understood phenomenon in orogenic-type mineral systems, partly because fluids in these systems are considered to have relatively low gold solubilities and are unlikely to generate high gold concentrations. The world-class Obuasi gold deposit, Ghana, has gold-rich arsenopyrite spatially associated with quartz veins, which have extremely high, localised concentrations of native gold, contained in microcrack networks within the quartz veins where they are folded. Here, we examine selected samples from Obuasi using a novel combination of quantitative electron backscatter diffraction analysis, ion microprobe imaging, synchrotron XFM mapping and geochemical modelling to investigate the origin of the unusually high gold concentrations. The auriferous arsenopyrites are shown to have undergone partial replacement (~15%) by Au-poor, nickeliferous arsenopyrite, during localised crystal-plastic deformation, intragranular microfracture and metamorphism (340-460 °C, 2 kbars). Our results show the dominant replacement mechanism was pseudomorphic dissolution-reprecipitation, driven by small volumes of an infiltrating fluid that had relatively low fS2 and carried aqueous NiCl2. We find that arsenopyrite replacement produced strong chemical gradients at crystal-fluid interfaces due to an increase in fS2 during reaction, which enabled efficient removal of gold to the fluid phase and development of anomalously gold-rich fluid (potentially 10 ppm or more depending on sulphur concentration). This process was facilitated by precipitation of ankerite, which removed CO2 from the fluid, increasing the relative proportion of sulphur for gold complexation and inhibited additional quartz precipitation. Gold re-precipitation occurred over distances of 10 µm to several tens of metres and was likely a result of sulphur activity reduction through precipitation of pyrite and other sulphides. We suggest this late remobilisation process may be relatively common in orogenic belts containing abundant mafic/ultramafic rocks, which act as a source of Ni and Co scavenged by chloride-bearing fluids. Both the preference of the arsenopyrite crystal structure for Ni and Co, rather than gold, and the release of sulphur during reaction, can drive gold remobilisation in many deposits across broad regions

Teaching in preschool : A qualitative study of how preschool teachers, preschool managers and head of operations interpret the concept of teaching

In 2011 pre-schools began reporting to the Education Department and were then subject to the school law. Pre-school’s entry into the school system meant that the concept of education became part of the pre-school’s activities. This is also to be implemented into the preschool curriculum. This study has examined how pre-school teachers, pre-school managers and heads of operations interpret the concept of "teaching" in the pre-school context. Respondents that were interviewed were familiar with the subject, due to the fact that they are part of a nationwide teaching project and they themselves work on implementing the concept of teaching in their operations. The aim has been to establish how the three professions interpret the concept and work with it in practice. The study is based on a social constructivist perspective where we chose to focus on how the concept of teaching is constructed and reconstructed using the social linguistic interaction and the interaction between respondents. As a research method, we have used qualitative group interviews. The empirical data has been analysed using the theoretical lens of social constructivism. The results showed that the term "teaching" was unclear when it is referred to pre-schools and did not have a specific definition in the pre-school context. The concept was understood differently by the three professions. The respondents argued that the implementation of the concept in the pre-schools took place in diverse ways. They confirmed that it is a long-term process that will take time to fully implement. Another conclusion that the authors drew was 2 that there was a gap between practice and theory. This was because the heads of operations and pre-school managers had a theoretical view of "teaching" while the pre-school teachers had a practical view.

Evaporitic brines and copper-sulphide ore genesis at Jbel Haïmer (Central Jebilet, Morocco)

International audienceThe Jbel Haïmer copper-sulphide mineralisation occurs at 20 km north of Marrakesh in the Variscan Jebilet massif, Morocco. Most of the ores (up to 3.9 wt. % Cu, ≤ 38 ppm Ag, and up to 2.9 ppm Au) occur as impregnations of NE-SW fault/fracture zones and related tectonic breccia. Two independent stages of fluid circulation and mineral deposition are distinguished. First, Late Variscan high temperature-low pressure metamorphism synchronous of granite intrusion induced percolation of C-H-O-N hydrothermal fluids throughout faults and shear zones. The drop in pressure from lithostatic down to hydrostatic values at temperatures around 350 ± 50°C triggered quartz precipitation associated with minor Sn-As-(Co-Ni) deposits and finally brecciation. The second stage, more recent than Triassic, consists in the deposition of quartz + carbonates, followed by Cu-(Pb-Zn) sulphides (±Ag-Au alloys) in fractures crosscutting 240 Ma microdiorite dikes. Mixing of evaporitic brines likely coming from Triassic formations with low salinity aqueous fluids was responsible for Cu-sulphide deposition at temperatures of around 220-280°C at a depth of 4-5 km. These base metal-rich brines are similar to those from the nearby Roc Blanc Ag-deposit and several other silver and base metal deposits in Morocco, considered as having circulated during the Central Atlantic Ocean opening

Mineralogy and ore fluid chemistry of the Roc Blanc Ag deposit, Jebilet Hercynian massif, Morocco

International audienceThe Roc Blanc Ag deposit is located about 20 km north of Marrakesh city (Morocco) in the Jebilet Hercynianmassif. The ore bodies consist of N-S to NE-SW quartz (±carbonates) veins hosted by the Sarhlefmarine sediments. These series, deposited in a Devonian-Carboniferous rift basin context, weredeformed during the Hercynian orogeny, and submitted to low-grade regional metamorphism.Two major stages of fluid circulation and metal deposition are distinguished on the basis of mineralogicaland paleo-fluid studies carried out on quartz and dolomite (microthermometry, Raman spectroscopy,LA-ICP-MS on individual inclusions, and O, H stable isotope data): (i) an early Fe-As stage,characterized by the circulation of metamorphic aqueous-carbonic fluids, under P-T conditions lowerthan 200 MPa ± 20 MPa and 400 C respectively, along N-S structures; (ii) the ore stage, characterized bythe circulation of a Na-Mg-K ± Ca high salinity brine, poor in gas but rich in metals such as Fe, Sr, Ba, Zn,Pb, ± Cu (salinity ranging from 19.6 wt% to likely more than 30 wt% NaCl equiv.) and the deposition of asphalerite/dolomite-calcite assemblage; such a fluid likely evolved to a Na-K-(Ca-Mg)-Ag brine, withsignificant Pb and Sb concentrations and lower Sr, Ba and Zn concentrations than in the preceding fluid(salinity up to 19.4 wt% NaCl equiv.). The Ag content of the second mineralizing brine ranges from0.9 mmol/kg to 9.4 mmol/kg solution (100 ppme1000 ppm), whereas the base metal brine is generallyAg poor (up to 1.3 mmol/kg solution: 140 ppm). Dilution of the Ag brine by low salinity fluids (<6 wt%NaCl equiv., and Th from 130 to 230 C) seems to be the main driving mechanism for the Ag oredeposition at Roc Blanc, with a possible involvement of cooling and reduction reactions in black schists.Base metal and Ag fluids may have circulated at average temperatures around 200 ± 30 C or slightlyhigher and under hydrostatic pressures, along dominant E-W structures. The ore forming model proposedfor the Roc Blanc deposit is: (i) the penetration of sedimentary brines coming from the adjacentbasins into the basement (i.e. Hercynian formations), where they extracted Ag probably from abundantmafic rocks; ii) the ore deposition in structural traps below the post Hercynian unconformity thanks tobrine mixing with low salinity fluids. The fluid circulation probably is related to the Atlasic rifting coevalwith the Atlantic Triassic opening. Such a model contrasts with the previous one relating the Roc Blanc tothe Hercynian granitic intrusions in the Jebilet. Ag deposition occurred during reworking of the earlystructures associated with the Hercynian orogenic events and metamorphic fluid circulation which led tothe early Fe-As uneconomic stages forming the main N-S quartz veins. Similarities between The RocBlanc Ag deposit and the major Ag deposits from Anti-Atlas south of Morocco strongly suggest that theyresulted from a unique and large fluid circulation event and a major period of metal deposition

Mineralization of water resources of Roc-Blanc watershed (Morocco)

International audienc