IN-SITU MONAZITE GEOCHRONOLOGY OF THE CARTHAGE-COLTON SHEAR ZONE: NEW CONSTRAINTS ON MAGMATISM, METAMORPHISM, AND DEFORMATION ALONG A MAJOR TECTONIC BOUNDARY IN THE ADIRONDACKS

2020 ◽  
Author(s):  
Erkan Toraman ◽  
◽  
Jeffrey R. Chiarenzelli ◽  
Michael L. Williams ◽  
M.J. Jercinovic
Keyword(s):  
Shear Zone ◽  
Tectonic Boundary

Studies on radionuclide transport behaviour–The next generation of in-situ experiments at the Grimsel Test Site

2009 ◽  
Vol 1193 ◽  
Author(s):  
Andrew James Martin ◽  
Ingo Blechschmidt
Keyword(s):  
Shear Zone ◽  
Diffusion Processes ◽  
Test Site ◽  
Core Material ◽  
Laboratory Studies ◽  
Grimsel Test Site ◽  
And Migration ◽  
Colloid Formation

AbstractTwo recent ongoing major projects at the Grimsel Test Site (GTS) (www.grimsel.com) that were initiated to simulate the long-term behaviour of radionuclides in the repository near-field and the surrounding host rock are presented: the Colloid Formation and Migration (CFM) project, which focuses on colloid generation and migration from a bentonite source doped with radionuclides and the Long-Term Diffusion (LTD) project, which aims at in-situ verification and understanding of the processes that control the long-term diffusion of repository-relevant radionuclides. So far, the CFM project has principally involved: development and implementation of a state-of-the-art sealing concept to control hydraulic gradients in a shear zone to imitate repository-relevant conditions; extensive laboratory studies to examine bentonite erosion and colloid formation in a shear zone; and, development of models to estimate colloid formation and migration. The next stage will be to assess the behavior of bentonite colloids generated from a radionuclide spiked bentonite source-term emplaced into the controlled flow field of the shear zone. This will be coupled with further extensive laboratory studies in order to refine and evaluate the colloid models currently used in performance assessments. The LTD project consists of: a monopole diffusion experiment where weakly sorbing and non-sorbing radionuclides (3H, 22Na, 131I, 134Cs) have been circulating and diffusing into undisturbed rock matrix since June 2007; experiments to characterise pore space geometry, including determination of in-situ porosity with 14C doped MMA resin for comparison with laboratory derived data; a study of natural tracers to elucidate evidence of long-term diffusion processes; and, an investigation of the in-situ matrix diffusion paths in core material from earlier GTS experiments. Future experiments will focus on diffusion processes starting from a water-conducting feature under realistic boundary conditions.

Controlled displacement-rate in situ shear tests with pore pressure measurements

1985 ◽  
Vol 22 (1) ◽  
pp. 136-142 ◽  
Author(s):  
F. S. Shuri ◽  
D. D. Driscoll ◽  
S. J. Garner
Keyword(s):  
Shear Strength ◽  
Pore Pressure ◽  
Shear Zone ◽  
Large Scale ◽  
Bedding Plane ◽  
Western Canada ◽  
Shear Tests ◽  
Plane Shear ◽  
Clay Seam

Two large-scale in situ shear tests were conducted at a damsite in western Canada. The rock at the site is a Cretaceous shale containing a thin clay seam tentatively identified as a bedding-plane shear zone. The material in this seam is significantly weaker than the intact rock and influences the design of certain features of the dam and structures. In order to provide shear strength data for design, two large blocks of shale were sheared along the clay seam. These tests differed from conventional in situ shear tests in two significant ways: the rate of shear displacement was strictly controlled, and pore pressures (both positive and negative) in the shear zone were carefully monitored throughout the test. This note presents the material properties of the shear zone, describes the test equipment and techniques, and discusses the results obtained. Key words: shear strength, in situ testing, pore pressure, shale.

scholarly journals Geology and tectonics of the Central Crystallines of northeastern Kumaun Himalaya, India

1998 ◽  
Vol 18 ◽  
Author(s):  
S. K. Paul
Keyword(s):  
Shear Zone ◽  
Normal Faults ◽  
Sedimentary Sequence ◽  
Main Central Thrust ◽  
The North ◽  
Northern Portion ◽  
Slip Displacement ◽  
Tectonic Boundary ◽  
Shear Planes ◽  
Extensional Structures

Four major geo-tectonic domains are encountered in the northeastern Kurnaun Himalaya between the Ramganga and Kali rivers. These tectonic domains are: (1) Sedimentary Terrain of the south, (2) Lower Central Crystallines, (3) Upper Central Crystallines, and (4) Tethyan Supergroup in the north. The Sedimentary Terrain comprises of the Berinag, Damtha and Tejam groups. The Lower Central Crystallinel are divided into Rungling and Munsiari formations, separated by a thin lensoidal wedge of sedimentary sequence of the Sirdang Sedimentary Zone, which is the continuation of the Nawakot Complex in western Nepal. The rocks of the Nawakot Complex wrap around the Chhiplakot Crystallines of the Munsiari Formation in Nepal and join with the Berinag Formation in northeastern Kumaun region. The Munsiari Formation has been divided into Phalyati, Baram, Chhiplakot and Khet members.The Upper Central Crystallines are represented by the rocks of the Vaikrita Group, and form the basement for the Tethyan sedimentary sequence. The Vaikrita Group is divided into four formations namely Joshimath, Pandukeshwar, Pindari and Martoli. The Joshimath Formation is further subdivided into Dar and Sela members whereas the Martoli Formation is subdivided into Budhi Schist and Dugtu members. The southern contact of the Munsiari Formation with the Lesser Himalayan sedimentary sequence forms a tectonic boundary designated as the Munsiari Thrust or MCT I. The southern contact of the Rungling Formation with the rocks of the Sirdang Sedimentary Zone forms another tectonic boundary designated as the Rungling Thrust or MCT II. The Munsiari Thrust (MCT I) has been interpreted to terminate near Chainpur in western Nepal at its branch point. The contact between the Upper Central Crystallines and the Lower Central Crystallines is designated as the Vaikrita Thrust or Main Central Thrust (MCT). The quartzite of the Berinag Formation exposed in the Sirdang Sedimentary Zone thrust over the Munsiari Formation along the Pangla Thrust. The northern part of the Martoli Formation of the Vaikrita Group is characterised by concordant relationship with the Ralam Conglomerate and also the Garbayang Formation of the Tethyan Super Group. Either side of this contact zone is characterised by a series of minor southward thrusts and associated shear planes, which are subsequently cut by a series of normal faults and related shear planes exhibiting down to the NE oblique slip displacement. The shear zone containing contractional and superposed extensional structures at the northern portion of the Vaikrita Group and at the basal part of the Tethyan Supergroup is designated as Tethyan Shear Zone.

New age constraints on the Lan Sang gneiss complex, Thailand, and the timing of activity of the Mae Ping shear zone from in-situ and depth-profile zircon and monazite U-Th-Pb geochronology

2019 ◽  
Vol 181 ◽  
pp. 103886 ◽  
Author(s):  
Jürgen E. Österle ◽  
Urs Klötzli ◽  
Daniel F. Stockli ◽  
Markus Palzer-Khomenko ◽  
Pitsanupong Kanjanapayont
Keyword(s):  
Shear Zone ◽  
Depth Profile ◽  
New Age ◽  
Gneiss Complex ◽  
Age Constraints

Polyphase gold mineralisation at the Yaou deposit, French Guiana

2021 ◽  
pp. SP516-2020-29
Author(s):  
Vincent Combes ◽  
Aurélien Eglinger ◽  
Anne-Sylvie Andre-Mayer ◽  
Yoram Teitler ◽  
Arnauld Heuret ◽  
...  
Keyword(s):  
Shear Zone ◽  
French Guiana ◽  
Primary Source ◽  
Gold Deposits ◽  
Low Grade ◽  
Gold Content ◽  
Icp Ms ◽  
Multiple Deformation ◽  
Penetrative Foliation

AbstractThe Yaou deposit, located in French Guiana within the Guiana Shield, is one of the most promising gold deposits of the regional Palaeoproterozoic greenstone belt. It displays numerous quartz monzodiorite bodies aligned along a sinistral shear zone where a five-deformation phases model is established at the camp scale. The ductile D1/2YA phase is responsible for the main penetrative foliation while the D3YA phase is related to shearing. An intrusive event is identified as being pre to syn-D3YA. The following phase D4YA represents a brittle quartz-carbonate veining set hosted preferentially within intrusive bodies and along the shear zone. A local D5YA brecciation event crosscuts the D4YA veins. Among this deformation history, two auriferous events (D3YA and D4YA) control the overall grade of the Yaou gold deposit. More specifically, most of the Au grade is associated with the main economic D4YA veining event, where the gold is visible and linked to Py4 within an ankerite/hematite rich alteration halo. At the microscopic scale, results of in situ analyses using LA-ICP-MS on pyrite show that metasediment-hosted Py0 is a primary source of submicroscopic gold having a low contribution to the total endowment. Py3 shows some gold content due to possible remobilisation of AuD0YA. Gold in Py4 is found as submicroscopic gold, as micro-inclusions and as infilling fractures in association with elements such as Te, Ag and Bi. Most contribution to the Au grade is from micro-inclusions and, to a lesser extent, from free and submicroscopic gold. The ore shoot locations are lithologically controlled for AuD0YA (metasedimentary unit-hosted), structurally controlled (shear zone-hosted) for AuD3YA and rheologically controlled for the AuD4YA (intrusion-hosted). The deposit is clearly polyphase both at the macroscopic and the microscopic scales, invisible gold is associated with As whereas visible gold is observed as inclusions in pyrite with high contents of Ag, Te and Bi. We define an early low-grade enrichment of AuD0YA to AuD3YA followed by a later high-grade event, AuD4YA supporting polyphase mineralisation processes. This study confirms that orogenic gold deposits can be formed by remobilisation and/or new gold inputs during multiple deformation, veining and hydrothermal events.

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