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This study demonstrates how mineralogy generated from spectroscopic visible, near, and shortwave infrared reflectance data, collected using rapid drill core logging systems, can be used to build one-, two- and three-dimensional models of the architecture of ore systems, with applications toward exploration and mining. In particular, this study examines both spectroscopic and traditional mining data (laboratory geochemistry and field geologist logging) from 180 drill holes through the Rocklea channel iron deposit in the Hamersley region of Western Australia. Valuable infrared reflectance spectroscopy-based mineralogy includes: the types and abundances of iron (oxyhydr-)oxides (hematite, vitreous goethite, and ochreous goethite); clays (well- and poorly ordered kaolin, Al and Fe smectite); and carbonates (calcite and dolomite). Algorithms to determine the abundance and composition of these minerals from infrared reflectance spectra were validated in an associated study by Haest et al. (2012) and were found to be accurate (e.g., root mean square error (RMSE) for Fe (oxyhydr-)oxide abundance prediction of 9.1 wt % Fe). Petrographic analysis and validated infrared reflectance spectroscopy-based mineralogy constrained the stratigraphy in the paleochannel and the Para genetic history of each horizon. The Rocklea channel iron deposit developed over weathered basalt and met sedimentary rocks, with an internal channel stratigraphy dominated from bottom to top by the following: (1) well-ordered (in situ) kaolinite and a partially deuaturated channel iron deposit, (2) poorly ordered (transported) kaolinite, (3) ochreous goethite with scarce ooidal textures, no clays, and late-stage vitreous goethite/silica replacement, (4) mostly poorly ordered kaolinite, and (5) calcrete with associated Fe smectite. The mineral Para genesis of the Rocklea deposit was compared against current models for channel iron deposit formation. A key finding is the relationship between parent rock composition, superimposed regolith cover, and channel iron deposit ore quality, which are linked through ground-water interactions and the physic-chemistries of both the parent rock and the deposit. This has implications for both exploration and ore deposit characterization: (1) ore-grade channel iron deposits can develop several kilometers downstream (50 km, in this case) from the proposed source rock areas above mafic volcanic and met sediments, (2) vitreous goethite, calcrete, Al and Fe smectite cover the Rocklea deposit and are proposed as potential vectors to channel iron deposit mineralization at depth, (3) improved mineralogy from hyperspeetral data in terms of iron (oxyhydr-) oxide and clay content/composition can improve iron ore resource delineation, iron ore processing (separation of vitreous and ochreous goethite), and pit design (differentiating "swelling" smectite (requiring pit walls with lower slopes) from kaolin or white mica). [ABSTRACT FROM AUTHOR]

Samples from the saprolite and extensive smectite zone (up to 25  m thick) of the Murrin Murrin lateritic nickel deposit, developed from serpentinised peridotites, were studied using optical microscopy, XRD, SEM and TEM-EDX. In the saprolite zone, the initial mesh-texture of the parent rock is still well preserved. The mineralogy is dominated by serpentine, smectite and maghemite. Two kinds of smectites occur in this zone: saponites and smectites with chemistries intermediate between two dioctahedral end-members (Fe nontronite, Fe montmorillonite) and a trioctahedral one (Mg + Ni saponite). In the smectite zone, serpentine and saponite completely disappear, however some relicts of the initial mesh-texture exist. Smectite and maghemite are the dominant minerals and goethite appears at the top of this zone. Smectites from the smectite zone have a complex chemistry which appears intermediate between four dioctahedral end-members (Fe Nontronite, Fe montmorillonite, Al beidellite, Al montmorillonite) and a trioctahedral one (Mg + Ni saponite). Smectites in fissures exhibit a greater variability in Al vs Fe + Cr content than smectites from plasma; this suggests a supply of Al by the percolating fluids. Nickel, essentially concentrated in the smectite zone (1.3 wt%), is located in the octahedral sheets of the plasma and fissure-smectites with Ni content up to 0.30 per half unit-cell. The oxygen and deuterium isotopic compositions of the smectites show that they crystallised at low temperature in contact with meteoric fluids. The δ 18 O values of Murrin Murrin smectites are negatively correlated with their Fe + Cr content. [ABSTRACT FROM AUTHOR]

Ni-bearing clays represent the main ore minerals in many laterite districts. Although the world-class Wingellina deposit (Western Australia) is an oxide-dominated ore, about 30% of the total Ni resources are hosted in the saprolitic section of the tenure, making the Ni-bearing clays a strategic target to increase the future ore reserves. In this study we present a detailed micro- to nanotextural TEM-HRTEM investigation of Ni-bearing smectites, which at Wingellina represent the main mineralogical species in the phyllosilicates assemblage. Ni-bearing smectites belong mainly to the dioctahedral (i.e. montmorillonite and nontronite) and to the trioctahedral (saponite and ferrosaponite) groups. The nanoscale TEM-HRTEM imaging indicates that Ni-bearing clays occur either as a replacement of the former clay suite (i.e. polygonal serpentine and chlorite) or as porous clay aggregates (i.e. PCA). Most of PCA was found closely associated with nanometric Co-bearing Mn-oxy-hydroxides. This finding not only provides a better understanding of the early stage formation of Mn-oxy-hydroxides in laterite systems, but is also important to better constrain the Co distribution and targeting within unconventional laterite ore facies. The nanoscale HRTEM imaging coupled with SAED allowed detecting minor Ni-bearing chlorite amounts, which were not found through previous XRPD-based techniques. Moreover, the paragenetic association of chlorite with primary serpentine suggests a pre-lateritic formation for chlorite. The detection of Ni-bearing trioctahedral smectite as alteration product of primary chlorite is of relevant importance, as it fills a gap in the knowledge of ore-formation processes occurring in smectite-endowed laterites. Unlabelled Image • TEM-HRTEM and AEM study of Ni-bearing smectites from the Wingellina deposit. • Ion-milling method unravels new aspects on the ore-formation processes in laterites. • Relevant genetic clues on the role of smectite in defining the Ni(Co) distribution. [ABSTRACT FROM AUTHOR]

The Wingellina Ni-Co laterite deposit (Metals X Ltd), located in Western Australia, hosts a resource of 168 Mt of ore at 0.98% Ni and 0.08% Co. The deposit is derived from the weathering of the mafic-ultramafic intrusion of the Giles Complex (Mesoproterozoic), consisting mainly of peridotite and gabbro. The lateritic profile comprehends two ore zones, characterized by the occurrence of oxy-hydroxides (i.e. limonite) and silicates (i.e. saprolite). The Co grade within the deposit is controlled by the MnO distribution, whose concentration is low in the saprolite zone (up to 0.036 wt% Co and 0.82 wt% MnO). Cobalt and MnO undergo a significant gain at the boundary between the saprolite and the limonite units, wherein they reach the highest concentration (up to 1.23 and 33.87 wt% Co and MnO, respectively). The Ni grade is more variable and is controlled by the geochemical (and mineralogical) evolution of the lateritic profile itself. The high Ni grades in the saprolite (up to 3.33 wt% Ni) occur below the so-called Mg-discontinuity, where the laterite profile has still remarkably high SiO2 and MgO concentrations (up to 62.87 and 23.14 wt% SiO2 and MgO, respectively). The transition between the saprolite and the limonite zone is characterized by a decrease in the MgO and SiO2 contents as well as by a variation in the Ni distribution, which in the upper zone is correlated with MnO and Fe2O3 (Putzolu et al., 2019). In fact, the occurrence of Mn-hydroxides and their mineralogy are the main factors that control at Wingellina the spatial distribution of the highest Co and Ni grades in the limonite unit. The highest Ni and Co grades occur in the so-called lithiophorite-asbolane intermediates, whereas other less abundant Mn-phases (i.e. romanèchite, ernienickelite-jianshuiite and K-birnessite) show lower ore concentrations. The Ni and Co concentration is higher in the late stage Mn-phases, resulting from the leaching of early formed Mn-hydroxides (Putzolu et al., 2018).Even though the limonite is the best developed zone in the Wingellina deposit, Ni reaches its highest concentration within the saprolite unit (Putzolu et al., 2019), where the mineralogy of the Ni-bearing phyllosilicates is heterogeneous and appears to be controlled by the geochemistry and mineralogy of the parent rock of the laterite. In particular, the dominant Ni-phyllosilicates in the gabbro-derived saprolite are dioctahedral smectites (e.g. montmorillonite), with trioctahedral type occurring as minor phases. The saprolite zone that develops from the ultramafic lithology (likely peridotite) has a more complex mineralogy. In this zone the Ni-bearing phases comprise both smectite clays (as nontronite and saponite) and hydrous Mg(Ni)-silicates (serpentine, chlorite and talc). The hydrothermally formed serpentine is commonly overprinted by Fe-oxy-hydroxides/quartz aggregates, as well as by the dioctahedral and trioctahedral smectites, whose genesis is associated with the lateritization stage. [ABSTRACT FROM AUTHOR]