Scheelite is a major (W)-bearing mineral enriched in rare earth elements (REEs) and is widely used to investigate the mineralization process, fluid source and redox environment of W deposits. In the Weijia skarn-type W deposit in South China, scheelite was formed during the greisen, retrograde skarn, oxidation, and sulfide-quartz vein stages. Various characteristics of cathodoluminescence (CL) images of scheelite grains (e.g., light to dark color, core-rim texture and oscillatory zonation) have recorded their detailed crystallization process. Scheelite grains formed in the greisen and retrograde skarn stages have similar LREE patterns, and the gradual fractionation in HREEs may be a result of the precipitation of garnet (And38-70Gr29-52Pr1-3) in the prograde skarn stage. In addition, the similar REE patterns of scheelite from the greisen stage and the granite porphyry pluton suggest a genetic relationship. The oxygen isotopic compositions of scheelite and quartz are all plotted near the edge of the magmatic fluid field, confirming their derivation from the same magmatic hydrothermal fluid. Elemental mapping and spot analyses using an electron probe microanalyzer indicated that extensive isomorphic substitution of W by molybdenum (Mo) occurs in scheelite, and the darker color in the CL images corresponds to a higher Mo content and lower W content. The Mo content of scheelite gradually increased from the greisen stage (mean = 0.46%), through the retrograde stage (mean = 2.89%), to the oxidation stage (mean = 19.8%), and then dropped sharply in the sulfide-quartz vein stage (mean = 0.20%), indicating a change in oxygen fugacity. Moreover, scheelite formed in the sulfide-quartz vein stage has an oscillating Mo content, thus implying a slight or periodical change in oxygen fugacity during the same mineralization stage.
The Min Shan and central and southern parts of the Longmen Mountains form the middle segment of the north trending earthquake zone at the eastern edge of the Tibetan Plateau. The Min Shan Mountains are a Cenozoic to Quaternary uplift zone that has undergone south directed block movements to produce the 1933 Diexi earthquake ( M = 7.5) on the Min Jiang Fault and the 1976 Songpan earthquake swarm ( M = 7.2, 6.7, 7.2) on the Huya Fault. The Min Jiang Fault on the western boundary of the uplift zone is dominated by reverse movement with a right‐lateral component. The Huya Fault on the eastern margin of the Min Shan Uplift Zone is also dominated by reverse movement but is associated with a left‐lateral component. The uplift and block movement of the Min Shan Mountains are probably related to the compression at the eastern end of the Kunlun Fault which is a major northwest trending strike‐slip fault within the Tibetan Plateau. Quaternary deformation in the Longmen Mountains is characterized by relatively continuous thrusting on major faults and Himalayan folding events in foreland basin deposits, and no earthquakes of M ≥ 7 have been recorded there.
Abstract The formation of the Songpan‐Garzê Fold Belt and the initiation of the terrestrial Sichuan Basin are related to closing of the Palaeo‐Tethys during the Late Triassic Indosinian orogeny. The Songpan‐Garzê Fold Belt is composed of Triassic (T 1 ‐ ‐ T 2 3 ) turbiditic deposits and Palaeozoic greywacke‐shale, whereas the Sichuan Basin consists of Sinian to middle Upper Triassic (T 2 3 ) platform carbonates and Upper Triassic (T 3X to Quaternary terrestrial elastics. Three principal deformation episodes during the Late Triassic (Norian to Rhaetian) were progressively localized towards the south‐eastern margin of the fold belt. D 1 was a SW‐directed shortening event, related to continuous subduction of the Palaeo‐Tethys, and produced NW‐trending structures. Differential strain between the fold belt and the Sichuan Basin was accommodated by sinistral shearing along a NE‐trending transitional zone during D 2 . D 3 SE‐directed compression was the result of collision between the Cimmerian and Eurasian Continents and initiated the Longmen Mountains Thrust‐Nappe Belt and terrestrial Sichuan Basin. Post‐D 3 deformation, related to SE‐directed thrusting in the Longmen Mountains, then propagated from hinterland to foreland. The Indosinian orogeny closed the Palaeo‐Tethys and terminated the marine conditions that dominated the early evolution of the intracratonic Sichuan Basin. Tectonic loading from the exhumed fold belt and Thrust‐Nappe Belt induced substantial subsidence in the Sichuan Basin, especially in the Western Sichuan Foreland Basin, resulting in the deposition of a terrestrial clastic sequence during Late Triassic (T 3X to Quaternary times. The foreland basin history comprises an early stage during the Late Triassic (T 3x 1–2 ), an over‐fill stage during the latest Triassic to Early Cretaceous (T 3X 3 ‐ K 1J ), and a shrinking stage from the Late Cretaceous to the Quaternary (K 2J ‐Q). These can be correlated with tectonic events in the Thrust‐Nappe Belt.
Research Article| March 01, 2001 Geometry and kinematics of large arcuate structures formed by impingement of rigid granitoids into greenstone belts during progressive shortening She Fa Chen; She Fa Chen 1Geological Survey of Western Australia, Kalgoorlie Regional Office, P.O. Box 1664, Kalgoorlie, Western Australia 6430, Australia Search for other works by this author on: GSW Google Scholar John W. Libby; John W. Libby 2Tarmoola Operations Pty. Ltd., A PacMin Corporation Limited Company, P.O. Box 67, Leonora, Western Australia 6438, Australia Search for other works by this author on: GSW Google Scholar John E. Greenfield; John E. Greenfield 3Geological Survey of Western Australia, 100 Plain Street, East Perth, Western Australia 6004, Australia Search for other works by this author on: GSW Google Scholar Stephen Wyche; Stephen Wyche 3Geological Survey of Western Australia, 100 Plain Street, East Perth, Western Australia 6004, Australia Search for other works by this author on: GSW Google Scholar Angela Riganti Angela Riganti 3Geological Survey of Western Australia, 100 Plain Street, East Perth, Western Australia 6004, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information She Fa Chen 1Geological Survey of Western Australia, Kalgoorlie Regional Office, P.O. Box 1664, Kalgoorlie, Western Australia 6430, Australia John W. Libby 2Tarmoola Operations Pty. Ltd., A PacMin Corporation Limited Company, P.O. Box 67, Leonora, Western Australia 6438, Australia John E. Greenfield 3Geological Survey of Western Australia, 100 Plain Street, East Perth, Western Australia 6004, Australia Stephen Wyche 3Geological Survey of Western Australia, 100 Plain Street, East Perth, Western Australia 6004, Australia Angela Riganti 3Geological Survey of Western Australia, 100 Plain Street, East Perth, Western Australia 6004, Australia Publisher: Geological Society of America Received: 17 Jul 2000 Revision Received: 29 Nov 2000 Accepted: 30 Nov 2000 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2001) 29 (3): 283–286. https://doi.org/10.1130/0091-7613(2001)029<0283:GAKOLA>2.0.CO;2 Article history Received: 17 Jul 2000 Revision Received: 29 Nov 2000 Accepted: 30 Nov 2000 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation She Fa Chen, John W. Libby, John E. Greenfield, Stephen Wyche, Angela Riganti; Geometry and kinematics of large arcuate structures formed by impingement of rigid granitoids into greenstone belts during progressive shortening. Geology 2001;; 29 (3): 283–286. doi: https://doi.org/10.1130/0091-7613(2001)029<0283:GAKOLA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Regional-scale arcuate structures in the central part of the Archean Yilgarn craton, Western Australia, were generated by impingement of competent granitoid blocks into less competent greenstone belts during progressive east-west shortening. Sinistral shear zones developed along northwest-trending margins of the granitoid blocks, whereas dextral shear zones developed along northeast-trending margins. In apex regions, these northeast- and northwest-trending shear zones are linked by north-trending contractional zones along which shortening was accommodated by the formation of folds and reverse faults in the greenstone belts and a coaxial flattening fabric in granitoid rocks. Lateral escape of the greenstone belts is indicated by the progressive rotation of early macroscopic folds into parallelism with the strike-slip shear zones during granitoid impingement. This recently recognized deformation style may have important tectonic implications for other Archean granite-greenstone terranes and where rock heterogeneity and competency differences are significant. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
The Pilbara and Yilgarn Cratons in Western Australia record the Earth?s early history from ca. 3.7 Ga to ca. 2.5 Ga. This paper highlights recent scientific work, and advances in understanding the similarity and differences in granitic rocks, greenstone stratigraphy, structural styles, and tectonic settings of the major granite?greenstone terranes within the cratons, and then discusses the crustal evolution trends from the Paleo- to Neoarchaean. We conclude that in the Pilbara and Yilgarn Cratons, the Paleoarchaean areas are characterized by vertical tectonics, whereas the Meso- to Neoarchaean areas are dominated by horizontal tectonics ? plate tectonic processes may have started in the Mesoarchaean.
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