scholarly journals The Geometry and Structural Analysis of the Gold Deposits of Chirano Mine

2016 ◽  
Vol 16 (2) ◽  
pp. 10-19
Author(s):  
K. Ackon-Wood ◽  
J. S. Y. Kuma ◽  
J. A. Yendaw
Keyword(s):  
Structural Analysis ◽  
Gold Deposit ◽  
Shear Zone ◽  
Gold Deposits ◽  
Drill Core ◽  
The South ◽  
Complex Interplay ◽  
The North ◽  
Structural Deformations

The Chirano Mine gold deposit is a typical example of a structurally controlled deposit developed along the Kumasi Basin and the Sefwi Belt margin structure. The area has undergone various regimes of structural deformations. Consequently, all the Chirano deposits are intimately associated with shears and faults along a single continuous structural corridor known as the Chirano Shear Zone (CSZ). The CSZ geometry has been categorised into three major zones namely: (i) Laminated veins in shears, (ii) Breccia and (iii) Ductile to brittle ductile zones. The shear veins trend NE-SW and N-S, are laminated and occur in the sheared fabric close to the footwall. Penetrative foliated zones varying from a few centimeters to several meters constitute the ductile to brittle-ductile structures. Gold grades are much higher within this zone. Analysis of cataclasis intensity recorded in drill core confirms a semi brittle form of deformation within the mineralised domain. The CSZ has different orientations in dip and strike from the south of the mining lease to the north. The subtle changes in orientation are deposit dependent. The structure has a sinuous shape and tends to pinch and swell. The current geometry and the distribution of stratigraphy and orebodies at Chirano is a manifestation of the complex interplay of magmatic and hydrothermal events in the area.  Keywords: Ductile, Brittle-Ductile, Breccia, Chirano Shear Zone, Chirano Lode Horizon

scholarly journals Crustal variability along the rifted/sheared East African margin: a review

2021 ◽  
Vol 41 (2) ◽  
Author(s):  
Maren Vormann ◽  
Wilfried Jokat
Keyword(s):  
East Africa ◽  
Shear Zone ◽  
Structural Changes ◽  
The South ◽  
East African ◽  
The North ◽  
Rifted Margins ◽  
Continental Block ◽  
Seismic Lines ◽  
Southeastern Madagascar

AbstractThe East African margin between the Somali Basin in the north and the Natal Basin in the south formed as a result of the Jurassic/Cretaceous dispersal of Gondwana. While the initial movements between East and West Gondwana left (oblique) rifted margins behind, the subsequent southward drift of East Gondwana from 157 Ma onwards created a major shear zone, the Davie Fracture Zone (DFZ), along East Africa. To document the structural variability of the DFZ, several deep seismic lines were acquired off northern Mozambique. The profiles clearly indicate the structural changes along the shear zone from an elevated continental block in the south (14°–20°S) to non-elevated basement covered by up to 6-km-thick sediments in the north (9°–13°S). Here, we compile the geological/geophysical knowledge of five profiles along East Africa and interpret them in the context of one of the latest kinematic reconstructions. A pre-rift position of the detached continental sliver of the Davie Ridge between Tanzania/Kenya and southeastern Madagascar fits to this kinematic reconstruction without general changes of the rotation poles.

scholarly journals The Dabie Extensional Tectonic System: Structural Framework

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Quanlin Hou ◽  
Hongyuan Zhang ◽  
Qing Liu ◽  
Jun Li ◽  
Yudong Wu
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Ultrahigh Pressure ◽  
Metamorphic Complex ◽  
The South ◽  
Magma Intrusion ◽  
The North ◽  
Extensional Tectonic ◽  
Mechanism Transition ◽  
Tectonic System

A previous study of the Dabie area has been supposed that a strong extensional event happened between the Yangtze and North China blocks. The entire extensional system is divided into the Northern Dabie metamorphic complex belt and the south extensional tectonic System according to geological and geochemical characteristics in our study. The Xiaotian-Mozitan shear zone in the north boundary of the north system is a thrust detachment, showing upper block sliding to the NNE, with a displacement of more than 56 km. However, in the south system, the shearing direction along the Shuihou-Wuhe and Taihu-Mamiao shear zones is tending towards SSE, whereas that along the Susong-Qingshuihe shear zone tending towards SW, with a displacement of about 12 km. Flinn index results of both the north and south extensional systems indicate that there is a shear mechanism transition from pure to simple, implying that the extensional event in the south tectonic system could be related to a magma intrusion in the Northern Dabie metamorphic complex belt. Two 40Ar-39Ar ages of mylonite rocks in the above mentioned shear zones yielded, separately, ~190 Ma and ~124 Ma, referring to a cooling age of ultrahigh-pressure rocks and an extensional era later.

scholarly journals A NEW GOLD ORE REGION IN TANZANIA

2018 ◽  
pp. 55-59
Author(s):  
V. Mykhailov ◽  
А. Tots
Keyword(s):  
Gold Deposit ◽  
Shear Zone ◽  
Gold Mineralization ◽  
Lake Victoria ◽  
Gold Deposits ◽  
Mobile Belt ◽  
Gold Content ◽  
Gold Ore ◽  
Metallogenic Zone ◽  
The Republic

Tanzania is one of the leading gold mining countries in the world and the discovery of new gold resources on its territory is an actual task. Known gold deposits are concentrated mainly in the northwest of the country, in the metallogenic zone of Lake Victoria, where they are associated with the Archean greenstone belts, and to a lesser extent – in the southwest, in the ore regions of Lupa and Mpanda, confined to the Ubendian Paleoproterozoic mobile belt. With regard to the eastern regions of Tanzania, where the Proterozoic structures of the Uzagaran mobile belt are developed, until recently in this region any significant manifestations of gold mineralization were not known. As a result of our research in the northern part of the Morogoro province of the Republic of Tanzania, a new previously unknown gold deposit Mananila was discovered. It is represented by a large volume, up to 400–450 m long, up to 60–80 m thick, mineralized shear zone over intensely leached and schistosed migmatites, gneisses, amphibolites, penetrated by echelon systems of quartz veins and veinlet, steeply dipping bodies of quartz breccia up to 1.0–1.5 m thick. Gold contents range from 0.61 to 8.11 g/t, the average zone content is 2.5–3.0 g/t. Parallel to the main zone, similar structures are developed on the site, although they are of lower thickness. The forecast resources of the deposit are estimated at 20 tons of gold. 2.8 km to the east from the Mananila field, the recently discovered Mazizi gold deposit is located, and a number of small occurrences of gold are also known in the region. All these objects are located within a large shear zone of the northeastern strike, up to 4–5 km width, over 20 km in length. This serves as the basis for the identification of a new gold ore region in the northern part of the Morogoro province of the United Republic of Tanzania, within the Proterozoic mobile belt of Usagaran, the possible gold content of which has never been previously discussed in geological literature.

Thermoluminescence of quartz from Shihu gold deposit, western Hebei province, China: some implications for gold exploration

2010 ◽  
Vol 2 (4) ◽  
Author(s):  
Ye Cao ◽  
Shengrong Li ◽  
Meijuan Yao ◽  
Huafeng Zhang
Keyword(s):  
Gold Deposit ◽  
Cross Sections ◽  
North China Craton ◽  
North China ◽  
Mineral Exploration ◽  
Gold Deposits ◽  
Quartz Veins ◽  
The North ◽  
Indicator Mineral ◽  
Gold Bearing

AbstractThermoluminescence (TL) of monomineralic separates have been widely used in various geosciences fields in order to trace the thermal history and aid in prospecting for gold deposits. Quartz is a ubiquitous mineral in the Shihu gold deposit, which is situated in the northern part of the Taihang orogenic belt in the North China craton (NCC). The deposit is hosted by ductile-brittle faults within an Archean metamorphic core complex of the Fuping Group. This deposit is characterized by gold-bearing quartz-polymetallic sulfides and quartz veins. New TL results have been obtained for quartz, in which four type-TL glow curves were identified. The gold-bearing quartz present type III glow curves that consist of two peak glow curves at the middle and high peak temperatures with the similar TL intensity. In addition, the cross-sections of peak temperatures and TL intensity highlight the valuable area where the Au-bearing quartz present weak TL intensity and low-middle peak temperatures. Our results significantly enhance the usefulness of quartz in metallogenic studies of the North China craton and as an indicator mineral in mineral exploration of the Taihang Mountain region.

Déformation coaxiale en bordure de la discontinuité structurale de Lyndhurst, sous-province de l'Abitibi

1992 ◽  
Vol 29 (4) ◽  
pp. 783-792 ◽  
Author(s):  
Jean-Yves Labbé ◽  
Real Daigneault ◽  
Pierre A. Cousineau
Keyword(s):  
Structural Analysis ◽  
Deformation Zone ◽  
Thrust Fault ◽  
The South ◽  
Mesoscopic Scale ◽  
The North ◽  
The Poor ◽  
Crenulation Cleavage ◽  
Deformation Regime ◽  
East West

The Lyndhurst discontinuity is a major east–west structure located some 40 km north of Rouyn–Noranda. It separates the rhyolitic and sedimentary units of the Hunter Mine Group to the north from the basalts of the Kinojévis Group to the south. Evidence of deformation is observed only in the rhyolites and sediments along the south edge of the Hunter Mine Group. The deformation zone is approximately 1 km wide and is continuous for about 30 km. The Kinojévis Group rocks are not deformed. Deformed rhyolites show a strong sericite and chlorite alteration of hydrothermal origin. The competency of the rhyolites is significantly reduced by the presence of these phyllosilicates, which results in the deformation being preferentially localized in the more altered rocks. Competency contrasts observed on a mesoscopic scale are also valid on the microscopic and megascopic scales. The structural analysis of the deformation zone reveals different arrays that characterize three distinct sectors. These arrays reflect competency contrasts of the lithology and a crenulation cleavage. The stretching lineation is generally steeply plunging. Although the deformation seems significant in a zone contiguous to the Lyndhurst discontinuity, the poor development of the stretching lineation, the preservation of the original crystalline shapes of phenocrysts in the rhyolites, and the constant symmetry of the pressure shadows suggest a global coaxial deformation. This deformation regime is difficult to reconcile with a compressive fault such as a thrust fault.

Seismic images of the Grenville Orogen in Ontario

1994 ◽  
Vol 31 (2) ◽  
pp. 293-307 ◽  
Author(s):  
D. J. White ◽  
R. M. Easton ◽  
N. G. Culshaw ◽  
B. Milkereit ◽  
D. A. Forsyth ◽  
...  
Keyword(s):  
Shear Zone ◽  
Seismic Data ◽  
Lower Crust ◽  
Wide Band ◽  
The South ◽  
Tectonic Zone ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Crustal Shortening ◽  
The North

In 1990, Lithoprobe acquired 240 km of seismic-reflection data across parts of the Central Gneiss Belt (CGB) and the Central Metasedimentary Belt (CMB) within the western Grenville Province of southern Ontario. Interpretation of these data in conjunction with geological constraints provided by bedrock mapping supports a model of northwest-directed thrusting and crustal shortening for the Grenville Orogen. Within the CGB, the Parry Sound shear zone is imaged as a 3 km wide zone of reflections dipping southeastward at 20–25° and soling at depths < 7 km in the north and < 3 km in the south beneath Parry Sound domain. Parry Sound domain and the immediately adjacent domains are underlain by a gently southeast-dipping reflective zone at 4.5–12.0 km depth interpreted as a detachment surface, likely associated with the central Britt shear zone. This zone may have accommodated northwesterly transport of Parry Sound, southern Britt, and northwestern Rosseau domains over Britt domain during Grenvillian thrusting.Within the CMB, the seismic data indicate that crustal shortening and imbrication have not been confined to domain and terrane boundaries, as presently defined. A 6 km wide band of reflections dips south at ~20° from the surface within Bancroft terrane, soling into a mid-crustal décollement beneath Elzevir terrane. Beneath and to the north of this planar reflective zone is a complex pattern of strong, south-dipping (10–40°) reflections that extends from the near surface to the lower crust above a less reflective wedge-shaped zone. The zone of complex reflectivity projects updip to the CMB boundary zone and into the CGB; together with the linear band of reflections affiliated with Bancroft terrane, they form the tectonized boundary between the CGB and the CMB. To the south of the linear reflective zone, prominent reflective packages are restricted to the middle and upper crust. The generally nonreflective uppermost crust beneath Elzevir terrane is underlain by a series of gently southeast-dipping, antiformal reflections that appear to sole into the mid-crustal décollement beneath Mazinaw terrane. These observations suggest that the collision between the CMB and the CGB resulted in a sequence of relatively thin (15–20 km thick) allochthonous terranes within the CMB being transported along a regional décollement and thrust northwestward over footwall rocks of the CGB along a penetratively deformed tectonic zone, while a lower crustal wedge may have delaminated the CMB lower crust. Crustal thickness where defined by the seismic data is 42.0–43.5 km in both the CGB and the CMB.

scholarly journals FIRST RECORD OF OSTRACODS IN THE ESTIVA FORMATION (PERNAMBUCO BASIN, UPPER CRETACEOUS), NORTHEAST OF BRAZIL

2021 ◽  
Vol 31 (1) ◽  
pp. 16-26
Author(s):  
Cecília Barros ◽  
Enelise Piovesan ◽  
Mário Lima Filho ◽  
Sonia Agostinho
Keyword(s):  
Literature Review ◽  
Continental Shelf ◽  
Shear Zone ◽  
Upper Cretaceous ◽  
First Record ◽  
The State ◽  
Basin Evolution ◽  
Southern Coast ◽  
The South ◽  
The North

The present work deals with the first record of ostracods in the Estiva Formation, Pernambuco Basin (Cupe, 1 LABIO-PE1 borehole). The Pernambuco Basin extends throughout the southern coast of the state of Pernambuco and is limited by the Pernambuco Shear Zone, in the north and by the Maragogi High, in the south. The Estiva Formation consists of continental shelf carbonates dated as Upper Cretaceous. The analysis and interpretation of the data were performed through literature review, stratigraphic data surveys, and sampling. The methodology used for the treatment of the samples consisted of the following steps: collection, weighing and fragmentation of the samples; washing and drying of the calcined materials; and screening and picking of the carbonatic microfossils. Rare ostracods were found, probably belonging to the brackish genus Fossocytheridea Swain & Brown, 1964. The recognition of the ostracod fauna and its paleoecology aims to contribute to the understanding of the Pernambuco Basin evolution.

The Mineralization Age of the Gupao Gold Deposit, Guangxi

2014 ◽  
Vol 501-504 ◽  
pp. 327-330
Author(s):  
Zhi Wu Zhang ◽  
Hui Li ◽  
Bin Yu ◽  
Shang Guo Zhou
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Tectonic Setting ◽  
Gold Deposits ◽  
Multiple Sources ◽  
The North ◽  
Mineralization Age ◽  
The Comparative Study ◽  
East West ◽  
Early Yanshanian

The Dayaoshan, which has nearly 200 gold deposits (or mineralization points), is one of the most important gold deposits distribution areas in Guangxi, and the Gupao gold deposit is an important representative one. Previous researches have carried out numerous works there to guide the gold prospecting work. Due to multiple episodes of gold mineralization and multiple sources materials in ore-forming, there are heated debates on the era of the mine, and the main mineralization age of the Gupao gold deposit is focused on the Caledonian or Early Yanshanian. According to the distribution characteristics of the gold ore body showing in the Zhilong, Gulinao, and Dawangding gold deposit, the discussion of macro-tectonic setting of the area, as well as the comparative study of surrounding gold deposits, we conclude that the main mineralization age of the Dawangding gold deposit is Early Yanshanian, and the main mineralization may be controlled by the nearly east-west trending fold which was caused by the north-south extrusion.

The ‘Historiated’ Neolithic Stele of Saint-Samson-sur-Rance (Côtes-d'Armor, France)

2017 ◽  
Vol 28 (2) ◽  
pp. 259-281 ◽  
Author(s):  
Serge Cassen ◽  
Valentin Grimaud ◽  
Laurent Lescop ◽  
Hervé Paitier ◽  
Carlos Rodríguez-Rellán ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Structured Light ◽  
Tidal Wave ◽  
Wild Animals ◽  
The South ◽  
The North ◽  
Structured Light Scanner ◽  
Human Figure ◽  
3D Methods ◽  
The Relationship

The stone of Saint-Samson is a Neolithic stele of 70 tons and 10 m of probable length. Its intriguing leaning position and its very regular morphology have aroused curiosity since medieval times. Three of its four faces—oriented towards the cardinal points—display engravings that were discovered in the 1970s. Now, a new recording protocol has combined 2D techniques for emphasizing the contrast of the engravings (oblique rotating lights) and 3D methods for restoring the volumes of the support (photogrammetry, structured-light scanner). The results obtained have made it possible to implement the first structural analysis of the stone. The north and west faces show an opposition between domestic (cattle, goats) and wild animals (suidae, cervidae, birds, cetaceans), depicted confronted and with their horns or tusks clearly visible. The south face was reserved for the human figure and for iconic artefacts (polished axe, throwing stick, ring disk, steering oar). The four faces have in common the presence of boats. The relationship linking the monument to waterways and the sea is approached by analysing both local legends and the phenomenon of the tidal wave.

Sign in / Sign up

Export Citation Format

Share Document