Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa

Abstract: We describe the physical context of the Dinaledi Chamber within the Rising Star cave, South Africa, which contains the fossils of Homo naledi. Approximately 1550 specimens of hominin remains have been recovered from at least 15 individuals, representing a small portion of the total fossil content. Macro-vertebrate fossils are exclusively H. naledi, and occur within clay-rich sediments derived from in situ weathering, and exogenous clay and silt, which entered the chamber through fractures that prevented passage of coarser-grained material. The chamber was always in the dark zone, and not accessible to non-hominins. Bone taphonomy indicates that hominin individuals reached the chamber complete, with disarticulation occurring during/after deposition. Hominins accumulated over time as older laminated mudstone units and sediment along the cave floor were eroded. Preliminary evidence is consistent with deliberate body disposal in a single location, by a hominin species other than Homo sapiens, at an as-yet unknown date

The geological setting of the indium-rich Baal Gammon and Isabel Sn-Cu-Zn deposits in the Herberton Mineral Field, Queensland, Australia

Base metal mineralization at the Baal Gammon and Isabel deposits of the Herberton Mineral Field (HMF) is hosted in metamorphosed greywacke beds in the Hodgkinson Formation, which were intruded by granite, porphyry dykes and overlain by volcanic rocks of the Kennedy Igneous Association during the Carboniferous and Permian. The tin mineralization at the Baal Gammon deposit is hosted by a silicified, chlorite-altered, quartz-feldspar porphyry (UNA Porphyry). The tin mineralization at the Isabel deposit is in polymetallic veins hosting disseminated cassiterite. Polymetallic sulfides (Cu-Zn) and indium (In) mineralization at both deposits overprint the tin mineralization. Chalcopyrite, sphalerite, and stannite host indium in the polymetallic sulfide assemblage at both deposits. Based on overprinting relationships, the timing of tin mineralization is related to the magmatic activity at ca. 320 Ma, whereas the sulfide and indium mineralization are most likely associated with the emplacement of porphyry dykes at ca. 290 Ma. The overall magmatic activity in the HMF spreads between ca. 365 and 280 Ma, with peaks at ca. 337, 322, 305, and 285 Ma. The change from tin mineralization at ca. 320 Ma to sulfide and indium mineralization at ca. 290 Ma indicates a transition from a compressive to an extensional tectonic regime

The Watershed tungsten deposit, NE Queensland, Australia: an example of a Permian metamorphic tungsten upgrade after a Carboniferous magmatic-hydrothermal mineralisation event

Tungsten is considered a strategic metal by various countries, including Australia. Between 1998 and 2016 Australia has been steadily increasing its tungsten production, but it is still far smaller than those of the main producers (e.g., China, Russia). Watershed with its current resources of 49.2 Mt averaging 0.14% WO3 is considered one of the biggest undeveloped tungsten deposits outside of China, and if developed would boost Australia’s tungsten production. We will be presenting the geological, geochemical and structural characteristics of the Watershed deposit, as well as the timing, mineral paragenesis and fluid characteristics of the mineralizing system; with the main goal of improving our understanding of the Watershed tungsten deposit and how to explore for similar deposits in northeast Queensland

Mineralogical distribution of germanium, gallium and indium at the Mt Carlton high-sulfidation epithermal deposit, NE Australia, and comparison with similar deposits worldwide

Germanium, gallium and indium are in high demand due to their growing usage in high-tech and green-tech applications. However, the mineralogy and the mechanisms of concentration of these critical elements in different types of hydrothermal ore deposits remain poorly constrained. We investigated the mineralogical distribution of Ge, Ga and In at the Mt Carlton high-sulfidation epithermal deposit in NE Australia, using electron probe microanalysis and laser ablation inductively-coupled plasma mass spectrometry. Parageneses from which selected minerals were analyzed include: Stage 1 acid sulfate alteration (alunite), Stage 2A high-sulfidation enargite mineralization (enargite, argyrodite, sphalerite, pyrite, barite), Stage 2B intermediate-sulfidation sphalerite mineralization (sphalerite, pyrite, galena) and Stage 3 hydrothermal void fill (dickite). Moderate to locally high concentrations of Ga were measured in Stage 1 alunite (up to 339 ppm) and in Stage 3 dickite (up to 150 ppm). The Stage 2A ores show enrichment in Ge, which is primarily associated with argyrodite (up to 6.95 wt % Ge) and Ge-bearing enargite (up to 2189 ppm Ge). Co-existing sphalerite has comparatively low Ge content (up to 143 ppm), while Ga (up to 1181 ppm) and In (up to 571 ppm) are higher. Sphalerite in Stage 2B contains up to 611 ppm Ge, 2829 ppm Ga and 2169 ppm In, and locally exhibits fine colloform bands of an uncharacterized Zn-In mineral with compositions close to CuZn2(In,Ga)S4. Barite, pyrite and galena which occur in association with Stage 2 mineralization were found to play negligible roles as carriers of Ge, Ga and In at Mt Carlton. Analyzed reference samples of enargite from seven similar deposits worldwide have average Ge concentrations ranging from 12 to 717 ppm (maximum 2679 ppm). The deposits from which samples showed high enrichment in critical elements in this study are all hosted in stratigraphic sequences that locally contain carbonaceous sedimentary rocks. In addition to magmatic-hydrothermal processes, such rocks could potentially be important for the concentration of critical elements in high-sulfidation epithermal deposits

Metamorphic diamond from the northeastern margin of Gondwana: Paradigm shifting implications for one of Earth’s largest orogens

We describe the first occurrence of diamond-facies ultrahigh pressure metamorphism along the Gondwana-Pacific margin of the Terra Australis Orogen. Metamorphic garnet grains from Ordovician metasediments along the Clarke River Fault in northeastern Queensland contain inclusions of diamond and quartz after coesite, as well as exsolution lamellae of rutile, apatite, amphibole, and silica. These features constrain minimum pressure-temperature conditions to >3.5 gigapascals and ~860°C, although peak pressure conditions may have exceeded 5 gigapascals. On the basis of these data, we interpret the Clarke River Fault to represent a Paleozoic suture zone and at least parts of the Terra Australis Orogen to have formed through classic Wilson cycle processes. The growth of the Terra Australis Orogen during the Paleozoic is largely attributed to accretionary style tectonics. These previously unknown findings indicate that the Terra Australis Orogen was not just a simple accretionary style orogen but rather a complex system with multiple tectonic styles operating in tandem including collisional tectonics

Genesis of copper mineralization in the polymetallic tin deposits from the Herberton Mineral Field, Queensland, Australia

The Herberton Mineral Field hosts multiple small-scale, polymetallic Sn-Cu and Sn-Zn deposits. The Baal Gammon and Isabel polymetallic deposits in the Herberton Mineral Field contain early Sn that is overprinted by sulfides. At Baal Gammon, the sulfide overprinting is Cu-In-rich, whereas Isabel is a Zn-Pb-In-rich system. These deposits are hosted in the meta-sedimentary rocks of the Hodgkinson Formation and the porphyry dikes and volcanic rocks of the Kennedy Igneous Association. Primary Sn in these deposits occurs as cassiterite, which was altered to stannite during sulfide mineralization. The sulfide ores from Baal Gammon consist of chalcopyrite, pyrrhotite, and minor sphalerite, and sphalerite, galena, and minor chalcopyrite are observed at Isabel. Chalcopyrite from Baal Gammon contains on average 609 ppm Ag, 1194 ppm In, and 1410 ppm Sn, whereas chalcopyrite from the Isabel deposit contains on average 2302 ppm Ag, 725 ppm In, and 1042 ppm Sn. Sulfur isotope (δ34S) measurements of in-situ chalcopyrite-pyrrhotite mineral pairs show limited variation and low values that are indicative of a magmatic sulfur source with limited interaction with sulfur from connate and meteoric fluids during mineralization. The chalcopyrite and pyrrhotite δ34S values at the Baal Gammon deposit vary between 0.99–1.91‰ and 1.35–2.48‰, respectively. The δ34S values at the Isabel deposit vary between 0.91–1.45‰ for chalcopyrite and 1.12–2.11‰ for pyrrhotite. The trace element composition of major sulfides and sulfur isotopes of chalcopyrite and pyrrhotite combined with thermodynamic modeling indicates that the mineralizing fluids at the Baal Gammon and Isabel deposits have an igneous source, where the metals were transported as metal-chloride complexes at low pH (< 5) and below ~ 300 °C. The source of these sulfide-rich mineralizing fluids is most likely derived from the magmatic activity associated with the emplacement of the Slaughter Yard Creek Volcanics during a period of crustal thinning between 300 and 280 Ma

The Lawn Hill annulus: An Ordovician meteorite impact into water-saturated dolomite

The Lawn Hill Impact Structure (LHIS) is located 250 km N of Mt Isa in NW Queensland, Australia, and is marked by a highly deformed dolomite annulus with an outer diameter of ~18 km, overlying low metamorphic grade siltstone, sandstone, and shale, along the NE margin of the Georgina Basin. This study provides detailed field observations from sections of the Lawn Hill annulus and adjacent areas that demonstrate a clear link between the deformation of the dolomite and the Lawn Hill impact. 40Ar-39Ar dating of impact-related melt particles provides a time of impact in the Ordovician (472 ± 8 Ma) when the Georgina Basin was an active depocenter. The timing and stratigraphic thickness of the dolomite sequence in the annulus suggest that there was possibly up to 300 m of additional sedimentary rocks on top of the currently exposed Thorntonia Limestone at the time of impact. The exposed annulus is remarkably well preserved, with preservation attributed to postimpact sedimentation. The LHIS has an atypical crater morphology with no central uplift. The heterogeneous target materials at Lawn Hill were probably low-strength, porous, and water-saturated, with all three properties affecting the crater morphology. The water-saturated nature of the carbonate unit at the time of impact is thought to have influenced the highly brecciated nature of the annulus, and restricted melt production. The impact timing raises the possibility that the Lawn Hill structure may be a member of a group of impacts resulting from an asteroid breakup that occurred in the mid-Ordovician (470 ± 6 Ma)

Trust \u3ci\u3eThe Key to Leading When Lives Are on the Line\u3c/i\u3e

The Hostage Rescue Team (HRT) of the Federal Bureau of Investigation was called in to assist the bureau\u27s Special Weapons and Tactics (SWAT) team in Memphis to apprehend a married couple wanted on drug trafficking charges. The fugitive couple and an adult son, all with criminal records, were believed to be living in trailers in a mountain valley where outsiders would be easily noticed. The fugitives were known to stockpile weapons and had vowed never to be taken alive by law enforcement. Thus the FBI considered them to be armed and extremely dangerous. Two HRT snipers along with two SWAT snipers were given the mission of positively identifying the fugitives and providing security and containment for the assault force. The snipers would have to travel several kilometers through wooded, mountainous terrain using night vision goggles (NVGs). The SWAT snipers did not have nighttime, overland movement capability, which is why HRT was brought in

The Paleozoic Mount Carlton deposit, Bowen Basin, Northeast Australia: shallow high-sulfidation epithermal Au-Ag-Cu mineralization formed during rifting

Mount Carlton is a Paleozoic high-sulfidation epithermal deposit located in the northern segment of the Bowen Basin, northeast Queensland, Australia. The deposit is hosted in Early Permian volcanic and sedimentary rocks, and an open-pit mining operation includes the Au-rich V2 pit in the northeast and the Ag-rich A39 pit in the southwest. Mineralization at Mt. Carlton occurred during active rifting, partly contemporaneously with the deposition of volcanic sediments in localized half-graben and graben basins. Steep normal faults and fracture networks related to the rifting acted as fluid conduits and localized cores of silicic alteration. The silicic cores transition outward to zones of quartz-alunite alteration, which are, in turn, enveloped by a zone of quartz-dickite-kaolinite alteration. Epithermal mineralization at Mt. Carlton developed in three stages: Cu-Au-Ag mineralization dominated by enargite was overprinted by Zn-Pb-Au-Ag mineralization dominated by sphalerite, which, in turn, was overprinted by Cu-Au-Ag mineralization dominated by tennantite. Proximal Au-Cu mineralization in the V2 pit occurs in networks of steep faults associated with veins and hydrothermal breccias within a massive rhyodacite porphyry. Three distinct ore zones (Eastern, Western, and Link) are aligned, en echelon, along a broadly E trending corridor. The Western ore zone continues along ~600-m strike length to the southwest into the A39 pit, and it shows a metal zonation, from proximal to distal, of Au-Cu → Cu-Zn-Pb-Ag → Ag-Pb-(Cu) → Ag. Distal Ag mineralization in the A39 pit is concentrated in a volcanolacustrine sedimentary sequence that overlies the rhyodacite porphyry. It occurs in a stratabound position oriented parallel to primary sedimentary layering and locally exhibits synsedimentary ore textures. Such textures are interpreted to have formed as mineralizing fluids discharged into what most likely were lakes developed within localized rift basins, at the same time that the volcanolacustrine sediments were deposited. At depth, equivalent ore textures were produced within open spaces in the structural roots of the rift basins. 40Ar/39Ar dating of hydrothermal alunite yielded an age range of 284 ± 7 to 277 ± 7 Ma, which links the formation of the Mt. Carlton deposit to the Early Permian back-arc rifting stage in the Bowen Basin. Prolonged extension provided rapid burial of the deposit beneath a postmineralization, volcanosedimentary cover, which was essential for the exceptional preservation of Mt. Carlton. The same extension caused displacement of the rock pile along a series of shallowly dipping detachment faults and segmentation and rotation of the ore zones across steeply dipping normal faults. This deformation would have displaced any underlying porphyry mineralization relative to the current location of Mt. Carlton

The Dugald River-type, shear zone hosted, Zn-Pb-Ag mineralisation, Mount Isa Inlier, Australia

The Dugald River Zn-Pb-Ag mine is situated in the Mount Isa Inlier, a globally significant base metal province. Zn-Pb deposits in the Mount Isa Inlier are stratabound with four main genetic models, including SEDEX-style, remobilised SEDEX, epigenetic and Broken Hill-type mineralisation applied to interpret their formation. We propose that the Zn-Pb-Ag mineralisation at Dugald River represents a unique, shear zone hosted deposit type that formed through a series of successive deformation events during the Paleoproterozoic Isan Orogeny that concentrated the mineralisation within the Dugald River Shear Zone during two main mineralising phases. The first phase of mineralisation occurred during regional D2 shortening, which is associated with the formation of large-scale F2 folds and a regionally penetrative S2 fabric. During this phase, progressive tightening of upright F2 folds resulted in several sets of secondary space accommodating quartz-carbonate veins that were progressively rotated into parallelism with the pervasive, steep, W-dipping S2 cleavage. The quartz-carbonate veins were coevally replaced by sulphides, which migrated to extensional sites (boudin necks and fold hinges) in tight folds. Thereby creating a sulphide-rich horizon within a developing high strain zone, which during D4 developed into the Dugald River Shear Zone. The second phase of mineralisation occurred during the regional D4 transpressional deformation event and resulted in significant metal enrichment and the current geometry of the ore bodies. The significant enrichment of the mineralisation during D4 resulted from further fold tightening within the high strain zone, which resulted in the attenuation and dismembering of folds and produced a transposed fabric (S4). The sulphide veins were transposed into parallelism with S4 forming sulphide-rich planar ore textures. Strain partitioning at the contact between the ductile deforming sulphide horizon and the brittle deforming slates resulted in the development of an anastomosing shear zone, known as the Dugald River Shear Zone. A right-handed releasing bend in the shear zone produced a dilational jog and a thick, high-grade ore body. The mobilisation of sulphides within the dilational jog involved fragmentation of sulphides and wall rock, brecciation, rotation and rolling of fragments, and the formation of durchbewegung texture