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The Achmmach tin mineralization (NE of the Moroccan Central Massif) is associated with tourmaline-rich alteration halos, veins, and faults hosted in sandstones and metapelites of the Upper Visean-Namurian. These deposits are reported to be late Hercynian in age and related to the emplacement of late-orogenic granite not outcropping in the studied area. Structural and paragenetic studies of the Achmmach tin deposit were conducted in order to establish a general model of the mineralization. From field constraints, the late Hercynian phase is marked by a transition from transpression to extension with deformation conditions evolving from ductile to brittle environments. The transpression (horizontal shortening direction roughly trending E-W) is coeval with the emplacement of the first tourmaline halos along several conjugated trends (N070, N020, and N120). Thereafter, a tourmaline-rich breccia formed in response to the fracturing of early tourmaline-altered rocks. Subsequently, during the extensional phase, these structures were reactivated as normal faults and breccias, allowing the formation of the main tin mineralization (cassiterite) associated with a wide variety of sulfides (arsenopyrite, chalcopyrite, sphalerite, galena, pyrrhotite, bismuthinite, pyrite, and stannite). This evolution ends with fluorite and carbonate deposition. The hydrothermal fluid flow velocity, calculated by applying statistical measures on the tourmaline growth bands, varies with the lithology. Values are lower in metapelites and higher in breccia. In the general evolution model proposed here, tourmaline alteration makes the rock more competent, allowing for brittle fracturing and generation of open space where the main Sn mineralization was precipitated. [ABSTRACT FROM AUTHOR]

Highlights: [•] “Memory loss” method measures the characteristics variations of ore during mineral processing. [•] “Memory loss” method can be a tool to characterize a given mineralogical processing. [•] Calculations require chemical compositions and residence time at each mineral processing steps. [•] Establish a database of the characteristic parameters of different processes. [Copyright &y& Elsevier]

The mining plant's wastes discharged in tailings ponds are under certain environmental conditions which cause chemical alteration, dispersion and mobility and therefore leading to a secondary mineralogy from the first one. In the district Zimapan, the orebody (skarn) containing Zn-Pb-Ag-(Cu) has generated a considerable amount of waste (50 years of disposal) stored in the ponds of San Miguel, Santa Maria and El Monte. The objective of this investigation was to determine the mineralogical neo-formation for the identification of the chemical behavior of metals in addition to environmental and health impact. An induction-coupled plasma spectrometry conducted revealed significant concentrations of trace elements in the chemical composition of the waste. The average concentrations were 13 135 mg/kg for As, 3 934 mg/kg for Pb, 11 363 mg/kg for mg/kg for Zn and 610 mg/kg for Cd. According to the mineralogical characterization using X-ray diffraction, calcite and quartz were identified as the majority mineral phases and gypsum, pyrite and sphalerite as the minority mineral phases as well as traces. During the completion of optical microscopy of polarization, sweeping electronics and electronic microsound, the neoformation of arseniates ferric (scorodite and symplesite), hydroxides and ferric sulfates and anglesite and cerusite was identified resulting from alteration, oxidation, sulphide hydrolysis such as arsenopyrite, pyrrhotite and galena. The sphalerite was classified as marmatite because of its iron content. As, Cd and Bi were found in particles of sulphosalts (boulangerite mineral); which can be released during meteorization; consequently, it was concluded that the waste is considered to be potentially toxic. [ABSTRACT FROM AUTHOR]

In order to better define the dependence of the mineral texture on flow, anisotropy of magnetic susceptibility (AMS) and microscopic observations have been performed on calcite-rich precipitations occurring in a horizontal pipe where the flow direction is clearly defined. A total of 65 cubes were cut from five slices, magnetic studies identified-pseudo-single domain magnetite as the major AMS carrier. Horizontal foliation characterizes the magnetic fabrics and the lineation is parallel to the pipe axis, that is, the flow direction. The origin of this lineation is discussed and is interpreted to be mainly the consequence of elongated pseudo-single domain magnetite. To complete the magnetic fabric studies, shape preferred orientation statistics were performed on 563 calcite sections in the (0001) calcite plane. It shows elongated shapes with a general orientation parallel to the pipe axis. The mean shape orientation is the average of two distinct subpopulations that deviated slightly from the pipe axis. Observation on calcite shapes and the direction of the magnetic lineation are coherent, suggesting that it is possible to track hydrothermal palaeocirculation using magnetic lineation and petrographic fabrics. [ABSTRACT FROM AUTHOR]