Geochemical evaluation of the in-situ regolith of Madengi hills of Dodoma, Tanzania. Implication on bedrock mapping and delineating gold mineralization target

2021 ◽  
pp. geochem2021-074
Author(s):  
Godson Godfray
Keyword(s):  
Gold Mineralization ◽  
Early Stage ◽  
Shear Zones ◽  
Soil Geochemistry ◽  
Residual Soils ◽  
Content Type ◽  
Geochemical Evaluation ◽  
Supplementary Material ◽  
Pathfinder Elements

Successful gold exploration projects depend on a piece of clear information on the association between gold, trace elements, and mineralization controlling factors. The use of soil geochemistry has been an important tool in pinpointing exploration targets during the early stage of exploration. This study aimed to establish the gold distribution, the elemental association between gold and its pathfinder elements such as Cu, Zn, Ag, Ni, Co, Mn, Fe, Cd, V, Cr, Ti, Sc, In, and Se and identify lithologies contributing to the overlying residual soils. From cluster analysis, a high similarity level of 53.93% has been shown with Ag, Cd, and Se at a distance level of 0.92. Au and Se have a similarity level of 65.87% and a distance level of 0.68, hence is proposed to be the most promising pathfinder element. PCA, FA, and the Pearson's correlation matrix of transformed data of V, Cu, Ni, Fe, Mn, Cr, and Co and a stronger correlation between Pb and U, Th, Na, K, Sn, Y, Ta and Be shows that source gold mineralization might be associated with both hornblende gneisses interlayered with quartzite, tonalite, and tonalitic orthogneiss. From the contour map and gridded map of Au and its pathfinder elements, it has been noted that their anomalies and target generated are localized in the Northern part of the area. The targets trend ESE to WNW nearly parallel to the shear zones as a controlling factor of Au mineralization emplacement.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5721965

Fluids sources in basement-hosted unconformity-uranium ore systems: tourmaline chemistry and boron isotopes from the Patterson Lake corridor deposits, Canada

2021 ◽  
pp. geochem2021-037
Author(s):  
E.G. Potter ◽  
C.J. Kelly ◽  
W.J. Davis ◽  
G. Chi ◽  
S-Y. Jiang ◽  
...  
Keyword(s):  
Shear Zones ◽  
Isotopic Signature ◽  
Strong Interactions ◽  
Content Type ◽  
B Values ◽  
Isotopic Signatures ◽  
Link Type ◽  
Basement Rocks ◽  
Supplementary Material ◽  
Over Time

The Patterson Lake corridor is a new uranium district located on the southwestern margin of the Athabasca Basin. Known resources extend almost one kilometer below the unconformity in graphite- and sulfide-bearing shear zones within highly altered metamorphic rocks. Despite different host rocks and greater depths below the unconformity, alteration assemblages (chlorite, illite, kaolinite, tourmaline and hematite), ore grades and textures are typical of unconformity-related deposits. This alteration includes at least three generations of Mg-rich tourmaline (magnesio-foitite). The boron isotopic composition of magnesio-foitite varies with generation: the earliest generation only observed in shallow samples from the Triple R deposit (Tur 1) contain the heaviest isotopic signature (δ11B ≈ +26 to +19 ‰), whereas subsequent generations (Tur 2, Tur 3) yield lighter and more homogeneous isotopic signatures (δ11B ≈ +17.5 to +19.9 ‰). These results are consistent with precipitation from low temperature, NaCl- and CaCl2-rich brine(s) derived from an isotopically heavy boron source (e.g. evaporated seawater) that interacted with tourmaline and silicates in the basement rocks and/or fluids derived from depth (with low δ11B values). The lower δ11B values in paragenetically later magnesio-foitite reflect greater contributions of basement-derived boron over time whereas minor compositional variations reflect local metal sources (e.g. Cr, V, Ti) and evolving fluid chemistry (decreasing Na and Ca, increasing Mg) over time. The δ11B and chemical variation in magnesio-foitite over time reinforce the strong interactions with basement rocks in these systems while supporting incursion of basinal brines well below the unconformity contact.Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathwaysSupplementary material:https://doi.org/10.6084/m9.figshare.c.5727555

Development of a photomicroscope method for in situ damage monitoring under ultrasonic fatigue test

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kai Tan ◽  
Victor Postel ◽  
Yujia Liu ◽  
Dongtong Yang ◽  
Sen Tang ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Early Stage ◽  
Strain Analysis ◽  
Infrared Camera ◽  
Small Crack ◽  
Image Correlation ◽  
Content Type ◽  
Damage Monitoring ◽  
Ultrasonic Fatigue

PurposeMechanical issues related to the information and growth of small cracks are considered to play a major role in very high cycle fatigue (VHCF) for metallic materials. Further efforts on better understanding in early stage of a crack are beneficial to estimating and preventing catastrophic damage for a long period service.Design/methodology/approachDependent on the ultrasonic loading system, a novel method of in situ photomicroscope is established to study the crack behaviors in VHCF regime.FindingsThis in situ photomicroscope method provides advantages in combination with fatigue damage monitoring at high magnification, a large number of cycles, and efficiency. Visional investigation with attached image proceeding code proves that the method has high resolution on both size and time, which permits reliable accuracy on small crack growth rate. It is observed that the crack propagation trends slower in the overall small crack stage down to the level of 10–11 m/cycle. Strain analysis relays on a real-time recording which is applied by using digital image correlation. Infrared camera recording indicates the method is also suitable for thermodynamic study while growth of damage.Originality/valueBenefiting from this method, it is more convenient and efficient to study the short crack propagation in VHCF regime.

Exhumation of the crustal-scale Gaoligong strike-slip shear belt in Southeast Asia

2021 ◽  
pp. jgs2021-038
Author(s):  
Yanlong Dong ◽  
Shuyun Cao ◽  
Franz Neubauer ◽  
Haobo Wang ◽  
Wenyuan Li ◽  
...  
Keyword(s):  
Shear Zone ◽  
Early Cretaceous ◽  
Vertical Motion ◽  
Shear Zones ◽  
Strike Slip ◽  
Western Boundary ◽  
The Tibetan Plateau ◽  
Content Type ◽  
Lateral Extrusion ◽  
Supplementary Material

Lateral extrusion of blocks is a well-known geological process during continent–continent collision, which always expresses by either brittle strike-slip faults or ductile shear zones. However, vertical motion along such fault systems remains poorly constrained. The Gaoligong shear zone (GLG-SZ) formed the western boundary of the Indochina block during the India–Eurasia collision, resulting in the exhumation of deep crustal rocks, including a large volume of syntectonic granites. Combined zircon U-Pb dating and 40Ar/39Ar thermochronology revealed that both the unfoliated and foliated granitic intrusions were emplaced during the Early Cretaceous (112–125 Ma), post-magmatic melting occurred from the Early Oligocene (ca. 35 Ma), and subsequent cooling during the Middle Miocene (ca. 13 Ma). The average emplacement depth of Early Cretaceous samples revealed that at least 15 km of hangingwall of the GLG-SZ must have been removed by vertical motion during shearing. Syn-shearing exhumation underlines the role of the lateral motion of the shear zone initiation by magma-assisted rheological weakening and exhumation at high ambient temperatures within the shear zone. A new model links magmatic channel flow underneath the Tibetan Plateau with magma intrusions and the high geothermal gradients along the shear belts, such as the GLG-SZ.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5598365

Low-Ti gabbroic pluton in Dali, SW China: new evidence for back-arc lithospheric melting inducing the early-stage magmatism of the Emeishan large igneous province

2021 ◽  
pp. jgs2020-224
Author(s):  
Bei Zhu ◽  
Zhaojie Guo ◽  
Shaonan Zhang ◽  
Ning Ye ◽  
Ziye Lu ◽  
...  
Keyword(s):  
Early Stage ◽  
Large Igneous Province ◽  
Spinel Peridotite ◽  
Heavy Rare Earth Element ◽  
Content Type ◽  
Igneous Province ◽  
Supplementary Material ◽  
Back Arc ◽  
Emeishan Lip ◽  
Yangtze Plate

The latest studies proved contribution of the Emeishan mantle plume (the widely-regarded origin of the Emeishan LIP in the western Yangtze Plate. LIP: large igneous province) to the Palaeo-Tethys subduction. However, whether the Palaeo-Tethys subduction oppositely affected the formation of the Emeishan LIP remains poorly understood. Here, we report geochronological, petrological, geochemical and isotopic studies of a gabbroic intrusion in this LIP, located in Jiangwei, the Dali area. The gabbro has a weighted mean SHRIMP U-Pb age of ∼262 Ma. Key geochemical features include Nb, Ta and Ti depletion; Th, U and Sr enrichment, low light/heavy rare earth element ratios and ∼0.707 87Sr/86Sr(t) and ∼-0.21 εNd(t) values. We conducted pMELTS thermodynamic modeling and batch melting calculations to evaluate the origin and evolution of the gabbro, based on real components of low-Ti picrites and xenolith of the Yangtze lithosphere. The results support 3% melting of a hydrated spinel peridotite source from the Yangtze lithosphere can produce magma equivalent to the gabbro components. Integrating this conclusion with tectonic background of the western Yangtze Plate and volcano-stratigraphic record of the Emeishan LIP, we infer the early-stage magmatism of the Emeishan LIP was triggered by Paleo-Tethys back-arc extension with fluid modification from subductional slab.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5433267

In-situ laser ablation Lu–Hf geochronology of garnet across the Western Gneiss Region: Campaign-style dating of metamorphism

2021 ◽  
pp. jgs2021-094
Author(s):  
Renée Tamblyn ◽  
Martin Hand ◽  
Alexander Simpson ◽  
Sarah Gilbert ◽  
Ben Wade ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Ultrahigh Pressure ◽  
Western Gneiss Region ◽  
Content Type ◽  
Link Type ◽  
Geological Processes ◽  
History Of ◽  
Supplementary Material ◽  
Wilson Cycle

The development of in-situ laser ablation Lu–Hf geochronology of apatite, xenotime and garnet has opened avenues to quickly and directly date geological processes. We demonstrate the first use of campaign-style in-situ Lu–Hf geochronology of garnet across the high- to ultrahigh-pressure Western Gneiss Region in Norway. Mafic eclogites from this region have been the focus of much work, and were clearly formed during continental subduction during the Caledonian Orogen. However, abundant quartzofeldspathic and pelitic lithologies record a more complex history, with some preserving polymetamorphic age data, and most containing no indication of high-pressure mineral assemblages formed during subduction. Twenty metapelitic and felsic samples spanning 160 lateral kilometers across the Western Gneiss Region have been analysed using garnet Lu–Hf geochronology. The results reveal Caledonian ages for the majority of the garnets, suggesting some quartzofeldspathic and metapelitic lithologies were reactive and grew garnet during high- to ultrahigh-pressure metamorphism. However, two ultrahigh-pressure eclogite locations, Verpeneset and Fjørtoft, preserve both Caledonian and Neoproterozoic-aged garnets. Despite significant uncertainties on some of the Lu–Hf geochronologic ages, laser ablation Lu–Hf efficiently identifies the polymetamorphic history of parts of the Western Gneiss Region, illustrating the effectiveness of this novel analytical method for rapid mapping of metamorphic ages.Thematic collection: This article is part of the Caledonian Wilson cycle collection available at: https://www.lyellcollection.org/cc/caledonian-wilson-cycleSupplementary material:https://doi.org/10.6084/m9.figshare.c.5715453

Did an earthquake located off Jersey trigger a mudflow preserving the only loess outcrop known under the seas?

2020 ◽  
Vol 177 (5) ◽  
pp. 911-922
Author(s):  
Jean-Pierre Lefort ◽  
Paul Chambers ◽  
Guzel Danukalova ◽  
Jean-Laurent Monnier ◽  
Eugenia Osipova ◽  
...  
Keyword(s):  
Slope Failure ◽  
Core Sample ◽  
Seismic Zone ◽  
Content Type ◽  
The Core ◽  
Loess Deposit ◽  
Mollusc Species ◽  
Supplementary Material ◽  
Rule Out

A 5 m long core sample, retrieved from between Jersey and the Cotentin (France) has been studied using different techniques. Between the lower part and the top, the core is a yellowish loess, a black mud and a grey shelly formation. The basal formation, which displays a typical loess granulometry, is the only loess found anywhere in situ on the subtidal seabed worldwide. Elsewhere, this fragile sediment has always been washed out by the successive Quaternary transgressions. The overlying mud formation, which displays characteristics of a landslide, sealed the loess deposit. Because this core has been sampled on the rim of a submarine valley located in front of a major onshore geological disruption, clearly associated with an active seismic zone, it is possible that an earthquake triggered a slope failure causing a gravity collapse of materials that protected the loess deposit from subsequent erosion, although we cannot completely rule out the effects of a large flood.Supplementary material: Tables showing the results of the pollen analysis and distribution of mollusc shells and other fossils in borehole O-VC15, and a figure showing the distribution of mollusc species in core O-VC15 and a possible reconstruction of the palaeoenvironment during sediment deposition are available at https://doi.org/10.6084/m9.figshare.c.4991753

The Saidu Gold Deposit of Southern Altai, China: Mineralizing Stages and Ore-Forming Fluids Evolution

2013 ◽  
Vol 734-737 ◽  
pp. 215-218
Author(s):  
Guo Rui Zhang ◽  
Jiu Hua Xu ◽  
Li Hua Shan ◽  
Hui Zhang ◽  
Xiao Feng Wei
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Early Stage ◽  
Shear Zones ◽  
Ductile Shear Zone ◽  
Tectonic Zone ◽  
Low Salinity ◽  
Ore Bodies ◽  
Evolution Characteristics ◽  
Homogenization Temperatures

The Saidu gold deposit is located in the northwest part of Ertix Tectonic Zone in Xinjiang. The ore bodies occur in altered mylonite zones within the Mar-kakol giant fault zone and are controlled by the ductile shear zone. The structural-metallogenic fluids of the early stage are characterized by mesothermal-hydrothermal CO2-N2-rich fluids, with homogenization temperatures of fluid inclusions being 252~408°C. The tectonic-metallogenic fluids at the middle stage are characterized by CO2-H2O fluids, with homogenization temperatures being 203~326°C. The fluids at the late stage were epithermal-mesothermal low salinity aqueous solutions, with homogenization temperatures being 120~221°C. The main gold mineralization was related to the post-orogenic extension environment, with the evolution characteristics corresponding to the evolution of shear zones.

Primary tissues dominated ground-level trunk diameter in Sigillaria: evidence from the Wuda Tuff, Inner Mongolia

2021 ◽  
pp. jgs2021-021
Author(s):  
Michael P. D'Antonio ◽  
C. Kevin Boyce ◽  
Wei-Ming Zhou ◽  
Hermann W. Pfefferkorn ◽  
Jun Wang
Keyword(s):  
Inner Mongolia ◽  
Ground Level ◽  
Early Ontogeny ◽  
Internal Anatomy ◽  
Living Plant ◽  
Content Type ◽  
Trunk Diameter ◽  
Primary Body ◽  
Supplementary Material

Arborescent lycopsid stumps are typically fossilized as casts, so that proximal anatomy is rarely available for study. This presents a roadblock for empirically reconstructing their early ontogeny, which requires knowledge of proximal tissue proportions. Here, we describe nine upright, in situ stump casts of Sigillaria from the earliest Permian Wuda Tuff, Inner Mongolia, China that preserve traces of internal anatomy. From these specimens, we interpret thin vasculature and periderm and a broad primary cortex within ∼50 cm of ground level in the living plant. These specimens support recent arguments that periderm production was limited in arborescent lycopsids and that the primary body reached its mature diameter close to ground level rather than distally further up the trunk.Supplementary material: additional figures of specimens and data regarding where measurements were made is available at https://doi.org/10.6084/m9.figshare.c.5558620

scholarly journals Structural Control on Banded Iron Formation (BIF) and Gold Mineralization at Abu Marawat Area, Central Eastern Desert, Egypt

2011 ◽  
Vol 22 (2) ◽  
pp. 155-183
Author(s):  
Mohamed K. El-Shafei Mohamed K. El-Shafei
Keyword(s):  
Structural Control ◽  
Gold Mineralization ◽  
Early Stage ◽  
Pure Shear ◽  
Shear Zones ◽  
Iron Formation ◽  
Low Grade ◽  
Brittle Deformation ◽  
Banded Iron Formation ◽  
Quartz Veins

Abu Marawat area is considered as a promising site for exploration of gold mineralization, where many ancient gold mines, hydrothermal alteration zones, and intervening quartz veins are present. This study is a field-based structural analysis that aims at revealing the relationship between mineral occurrences and local structural setting. The area is a part of a back-arc volcanosedimentary sequence associated with banded iron formation (BIF) that has undergone extensive ductile and brittle deformation history. This multiple deformation is manifested by four phases. D1 and D2 are the product of compressional stresses and are expressed by F1, F2 and F3 folds in low-grade regionally metamorphosed rocks. D1 was a progressive deformational phase started with F1 folds, which in a later stage were overprinted by F2 folds. It resulted from NW-SE-oriented pure shear and is associated with imbricate thrust stacks, which control the locations of listwanite bearing gold. NE-SW-oriented compressive stress during D2 is displayed by F3-slip folds at the early stage followed by N-S- to NW-trending dip-slip normal faults and related shear zones. Mineralized quartz veins (MQV) were developed post-D2 and pre-D3. Folding and refolding in addition to thrust movement play a significant role in shortening and thickening of the iron formation bands located at the summit of Gebel Abu Marawat. D3 and D4 are expressed by brittle deformation. D3 is displayed by conjugate shear planes represented by sinistral-NW-oriented and dextral-NE–oriented strike-slip faults that led to the dislocation and redistribution of gold mineraliztion associated with both MQV and listwanite. Barren quartz veins trending E-W were also developed along gash fractures formed during this phase of deformation.

scholarly journals The Nonesuch Formation Lagerstätte: a rare window into freshwater life one billion years ago

2020 ◽  
pp. jgs2020-133
Author(s):  
Paul K. Strother ◽  
Charles H. Wellman
Keyword(s):  
Early Stage ◽  
Cell Structure ◽  
Upper Peninsula ◽  
Content Type ◽  
Eukaryotic Diversity ◽  
Exceptional Preservation ◽  
Marine Deposits ◽  
Wide Range ◽  
Supplementary Material ◽  
Clastic Sedimentary

The Nonesuch Formation in the clastic sedimentary Oronto Group on the Keweenaw Peninsula of the Upper Peninsula, Michigan, USA most likely represents an ancient lake that formed between 1083 and 1070 Ma. Exceptional preservation, seen in palynological preparations, provides a snapshot of cell morphology, biological complexity and ecology at an early stage in the evolution of the eukaryotes. A wide range of unicellular organization is documented in both vegetative and encysted cell morphologies, but the extent to which multicellularity is developed seems very limited at this time. Overall, the Nonesuch microbiota, when viewed as a Lagerstätte, opens up a window onto the early evolution of unicellular eukaryotes, presenting an essential baseline of both eukaryotic diversity and cell structure well in advance of eukaryotic diversification documented in marine deposits from the later Neoproterozoic.Supplementary material: Materials and methods with a detailed specimen list are available at: https://doi.org/10.6084/m9.figshare.c.5183652

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