Geology of the Matthew Creek metamorphic zone, southeast British Columbia: a window into Middle Proterozoic metamorphism in the Purcell Basin

2000 ◽  
Vol 37 (7) ◽  
pp. 1073-1092 ◽  
Author(s):  
C RM McFarlane ◽  
D RM Pattison
Keyword(s):  
British Columbia ◽  
Transition Zone ◽  
Ductile Deformation ◽  
Low Grade ◽  
Core Zone ◽  
The Core ◽  
Pelitic Schist ◽  
Metamorphic Zone ◽  
Structural Dome ◽  
Middle Proterozoic

Southwest of Kimberley, southeastern British Columbia, the Matthew Creek metamorphic zone occupies the core of a structural dome in Mesoproterozoic rocks of the Lower Aldridge formation (lower Purcell Supergroup). It comprises (1) a core zone of ductilely deformed sillimanite-grade metapelites, thin foliated mafic sills, and sheared quartz-plagioclase-tourmaline pegmatites; and (2) a thin transition zone of ductilely deformed metasediments which marks a textural and metamorphic transition between the core zone and overlying regionally extensive, brittlely deformed, biotite-grade semipelitic Lower Aldridge formation metasediments and thick Moyie sills. The core zone and transition zone in combination cover an area of 30 km2. The deepest exposed rocks in the core zone have a strong foliation and lineation (D1 deformation) formed during late M1 metamorphism at conditions of 580–650°C and 3.5 ± 0.5 kbar. The timing of this metamorphic-structural episode is constrained to the interval 1352–1341 Ma based on near-concordant U–Pb ages from monazite in pelitic schist near the mouth of Matthew Creek. Later, weaker metamorphic and deformation episodes variably overprinted the rocks of the Matthew Creek metamorphic zone. The juxtaposition of low-grade, weakly deformed rocks above high-grade, strongly deformed rocks across a zone of ductile deformation is interpreted to be due to a subhorizontal shear zone.

Precambrian Zircon Age of Orthogneiss in the Shuswap Metamorphic Complex, British Columbia

1975 ◽  
Vol 12 (2) ◽  
pp. 326-332 ◽  
Author(s):  
R. K. Wanless ◽  
J. E. Reesor
Keyword(s):  
British Columbia ◽  
Metamorphic Complex ◽  
Gneiss Dome ◽  
Zircon Age ◽  
Core Zone ◽  
The Core ◽  
Basement Rocks ◽  
Proterozoic Basement ◽  
Shuswap Metamorphic Complex ◽  
Age Determinations

Pb-U age determinations carried out on zircon from granodiorite gneiss of the core zone of Thor-Odin gneiss dome have provided isotopic evidence for involvement of Proterozoic basement rocks in the Mesozoic structures of the Shuswap Metamorphic Complex. The study has revealed that the zircons originally crystallized [Formula: see text] ago and suffered an episodic loss of lead [Formula: see text] ago.

Superimposed low-grade metamorphism in the Mount Fisher area, southeastern British Columbia—implications for the East Kootenay orogeny

1982 ◽  
Vol 19 (3) ◽  
pp. 476-489 ◽  
Author(s):  
M. E. McMechan ◽  
R. A. Price
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Rocky Mountains ◽  
Regional Metamorphism ◽  
Low Grade ◽  
Canadian Cordillera ◽  
Windermere Supergroup ◽  
Granitic Intrusion ◽  
Block Faulting ◽  
Middle Proterozoic

Middle Proterozoic (~1500–1350 Ma) Belt–Purcell strata exposed in the Purcell and southwestern Rocky Mountains were affected by at least three distinct episodes of deformation and regional metamorphism. The oldest episode (1300–1350 Ma) apparently terminated Belt–Purcell sedimentation and involved folding, regional metamorphism, and granitic intrusion. The second episode (800–900 Ma) occurred during deposition of the Windermere Supergroup and involved uplift, block faulting, and low-grade regional metamorphism. Mesozoic–Cenozoic metamorphism, deformation, and plutonism overprinted the results of the earlier deformation and metamorphism.Illite crystallinity and muscovite polymorph ratios indicate that Purcell strata in the Mount Fisher area are in the lower green-schist to prehnite–pumpellyite facies of regional metamorphism. In the Steeples and Fisher blocks this metamorphism is related to structures that formed during the Late Cretaceous – Paleocene deformation. However, in the Sand Creek block the regional metamorphism is related to the development of a spaced cleavage that is folded by a Late Cretaceous – Paleocene nappe. Regional considerations suggest that this cleavage formed during the 1300–1350 Ma episode of deformation and metamorphism.The "East Kootenay orogeny" as currently defined embraces the two older episodes of tectonism. It is proposed that the term East Kootenay orogeny be restricted to designate the 1300–1350 Ma episode and that the term "Goat River orogeny" designate the 800–900 Ma episode of tectonism. The East Kootenay and Goat River orogenies appear to be correlative with the Racklan and Hayhook orogenies recognized in the northern Canadian Cordillera.

A Gravity Model for the Guichon Creek Batholith, South-central British Columbia

1973 ◽  
Vol 10 (6) ◽  
pp. 920-935 ◽  
Author(s):  
C. A. Ager ◽  
T. J. Ulrych ◽  
W. J. McMillan
Keyword(s):  
British Columbia ◽  
Gravity Model ◽  
Three Dimensional ◽  
Mineral Deposits ◽  
Low Grade ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
The Core ◽  
South Central ◽  
Surface Projection

The Guichon Creek batholith, located in south-central British Columbia, contains several large, low-grade copper deposits of considerable economic importance.A three dimensional model for the batholith has been proposed on the basis of a gravity survey conducted in 1971. Its gross shape can be likened to that of a flattened funnel-like structure with a tilted spout. The distribution of mineral deposits appears to be spatially related to the surface projection of the core of the batholith.

Direct Observation of Crystalline Ordering In Naturally Graphitized Carbon Produced by Low Grade Metamorphism

1977 ◽  
Vol 35 ◽  
pp. 162-163
Author(s):  
Thomas R. McKee ◽  
Peter R. Buseck
Keyword(s):  
Crystallite Size ◽  
Sedimentary Rocks ◽  
Carbonaceous Material ◽  
Low Grade ◽  
X Ray ◽  
Graphitized Carbon ◽  
Transmission Electron ◽  
Heat Treated ◽  
Commercial Carbon ◽  
Metamorphic Zone

Sediments commonly contain organic material which appears as refractory carbonaceous material in metamorphosed sedimentary rocks. Grew and others have shown that relative carbon content, crystallite size, X-ray crystallinity and development of well-ordered graphite crystal structure of the carbonaceous material increases with increasing metamorphic grade. The graphitization process is irreversible and appears to be continous from the amorphous to the completely graphitized stage. The most dramatic chemical and crystallographic changes take place within the chlorite metamorphic zone.The detailed X-ray investigation of crystallite size and crystalline ordering is complex and can best be investigated by other means such as high resolution transmission electron microscopy (HRTEM). The natural graphitization series is similar to that for heat-treated commercial carbon blacks, which have been successfully studied by HRTEM (Ban and others).

Determination of core zone of marine sanctuary in Bahoi Village, North Minahasa Regency

2013 ◽  
pp. 10
Author(s):  
Sonny Tasidjawa ◽  
Stephanus V Mandagi ◽  
Ridwan Lasabuda
Keyword(s):  
Conventional Method ◽  
Local Community ◽  
Marine Protected Area ◽  
Final Decision ◽  
Marine Biota ◽  
Small Community ◽  
Community Based ◽  
Simple Method ◽  
Core Zone ◽  
The Core

Bahoi village is located in West Likupang District of North Minahasa Regency. It is one of the villages that is included in the conservation network of North Sulawesi Province. A marine sanctuary has been established in this village in 2003 and it has been managed by local community, known as community-based marine sanctuary management, since then, this sanctuary has been in operation. As a small community-based marine protected area with lots of users, it requires an appropriate method to determine the Core Zone that allows an effective preservation of the marine biota. This is the driving factor of this study.  The purpose of this study is to examine the processes and output of determining the core zone of a Marine Sanctuary using a conventional method and Marxan Method. The conventional method is a simple method in determining a core zone such as using manta tow technique. While Marxan, it only requires input of data such as spatial and figures to generate information for determining the core zone. After comparing the processes of these two methods in the study site, it was found that Marxan method was more effective and more accurate with lower costs than the conventional one. In addition, the final decision of the core zone depended on the outcome of the village meetings when the conventional method was applied. This long process could be avoided when Marxan method was used. Therefore, it is highly recommended to use Marxan in determining core zones© Desa Bahoi terletak di Kecamatan Likupang Barat Kabupaten Minahasa Utara. Desa ini merupakan salah satu desa yang masuk dalam jejaringan kawasan konservasi di Provinsi Sulawesi Utara. Sebuah Daerah Perlindungan Laut telah didirikan di desa ini pada tahun 2003 dan dikelolah oleh masyarakat setempat, yang dikenal sebagai pengelolaan Daerah Perlindungan Laut Berbasis Masyarakat, sejak saat itu Daerah Perlindungan Laut ini telah beroperasi. Sebagai Daerah Perlindungan Laut Berbasis Masyarakat yang kecil namun memiliki banyak pengguna, diperlukan metode tepat yang akan menentukan Zona Inti yang memungkinkan pelestarian biota laut menjadi sangat efektif. Ini adalah faktor pendorong dari penelitian. Selanjutnya, tujuan dari penelitian ini adalah untuk mengkaji proses dan hasil penentuan zona inti Daerah Perlindungan Laut dengan menggunakan metode konvensional seperti survei manta tow dan marxan. Metode konvensional adalah metode sederhana dalam menentukan zona inti seperti teknik manta tow. Sedangkan marxan, hanya perlu memasukan data seperti spasial dan angka untuk menghasilkan informasi penentuan zona inti. Setelah membandingkan proses dari dua metode di lokasi penelitian, ditemukan bahwa metode marxan jauh lebih baik dari pada metode konvensional, karena lebih efektif, lebih akurat dengan biaya yang lebih rendah. Selain itu, keputusan akhir dari zona inti tergantung pada hasil rapat desa ketika metode konvensional diterapkan, proses panjang ini dapat dihindari jika metode marxan digunakan©

Abundance of coral-polyp-eating gastropods Drupella cornus in Bunaken National Park, Indonesia: indicating anthropogenic impact?

2013 ◽  
Vol 1 (1) ◽  
pp. 17
Author(s):  
Farnis B Boneka ◽  
N Gustaf F Mamangkey
Keyword(s):  
National Park ◽  
Anthropogenic Impact ◽  
Coral Cover ◽  
Human Intervention ◽  
Core Zone ◽  
The Core ◽  
Human Interventions ◽  
Coral Polyp ◽  
Intervention Zone ◽  
Drupella Cornus

Corallivorous gastropods, Drupella cornus are living in the Indo Pacific coral reefs. To assess the distribution of the snails at Bunaken National Park in Indonesia, a study has been conducted on three zones established in three main islands of the park: core, tourism, and exploitation zones. The zones represent degrees of human interventions in which the least intervention is for core zone, moderate for tourism zone and high for the exploitation zone. The results showed that degrees of human interventions are related to the density of snails where the least human intervention zone (the core zone) had low numbers of snails while the high human intervention (exploitation) zone had high numbers of snails. Three corals in the zones that were preferred by the snails were: Montipora spp., Acropora spp., and Porites spp. The numbers of snails living on the corals followed the percent of coral cover© Gastropod pemakan polip karang, Drupella cornus hidup di areal terumbu karang Indo-Pasifik. Untuk mengetahui distribusi dari siput di Taman Nasional Bunaken, sebuah studi telah dilakukan pada tiga zona yang ditetapkan di tiga pulau utama di taman nasional ini: zona inti, zona pariwisata, dan zona pemanfaatan. Hasil penelitian ini menunjukkan bahwa tinggi-rendahnya intervensi manusia berhubungan dengan kepadatan siput di mana zona yang memiliki intervensi terendah (zona inti) memiliki jumlah siput sedikit sementara zona dengan intervensi tertinggi (zone pemanfaatan) memiliki jumlah siput terbanyak. Tiga spesies karang di ketiga zona ini yang disukai oleh siput adalah Montipora spp., Acropora spp., and Porites spp. Jumlah siput yang hidup di karang mengikuti jumlah persen tutupan karang©

Ecotypic variation affects the conservation of North American badgers endangered along their northern range extent

2018 ◽  
Author(s):  
Richard D. Weir ◽  
Trevor A. Kinley ◽  
Richard W. Klafki ◽  
Clayton D. Apps
Keyword(s):  
British Columbia ◽  
Cause Of Death ◽  
Conservation Strategies ◽  
High Fecundity ◽  
Ecological Information ◽  
The Core ◽  
Ecotypic Variation ◽  
Sufficient Energy ◽  
Soil Deposits ◽  
Regional Conservation

This chapter is based on ecological information on 82 radio-tagged badgers (39 F, 43 M) among three study populations in British Columbia, Canada between 1996 and 2010, data that were collected to learn more about the ecology of badgers and consider how variation in their ecology might inform regional conservation strategies. The widely spaced, lower density prey and distribution of soil deposits suitable for digging in British Columbia likely required badgers to use substantially larger areas, relative to the core range, in which to acquire sufficient energy to survive and reproduce. Strikes from automobiles were the primary cause of death among all radio-tagged badgers and this source of mortality is pervasive throughout the limited distribution of badgers in British Columbia. Despite their potential for high fecundity, populations of badgers in British Columbia likely remain at considerable risk compared to those in the core of the species’ range.

scholarly journals Wave velocities in the earth's core

1958 ◽  
Vol 48 (4) ◽  
pp. 301-314
Author(s):  
B. Gutenberg
Keyword(s):  
Travel Time ◽  
Transition Zone ◽  
Southern California ◽  
Inner Core ◽  
Travel Times ◽  
Earth’S Core ◽  
Earth's Core ◽  
The Core ◽  
Wave Velocities

Abstract More than 700 seismograms of 39 shocks recorded mainly in southern California at epicentral distances between 105 and 140 degrees are used to investigate records of phases which have penetrated the earth's core. Properties of PKIKP, SKP, SKIKP, PKS, and PKIKS are discussed. Portions of travel-time curves of these phases are revised. Travel times of waves starting and ending at the surface of the core, and wave velocities in the core, are recalculated. Between about 1,500 and 1,200 km. from the earth's center in the transition zone from the liquid outer to the probably solid inner core, waves having lengths of the order of 10 km. travel faster than longer waves. This is probably caused by a rather rapid increase in viscosity toward the earth's center in this transition zone.

A geochronological framework for sedimentation and Mesoproterozoic tectono-magmatic activity in lower Belt–Purcell rocks exposed west of Kimberley, British Columbia

2015 ◽  
Vol 52 (7) ◽  
pp. 444-465 ◽  
Author(s):  
Christopher R.M. McFarlane
Keyword(s):  
British Columbia ◽  
Minor Component ◽  
Structural Level ◽  
Peraluminous Granite ◽  
Icp Ms ◽  
Ductile Shearing ◽  
History Of ◽  
Metamorphic Zone ◽  
A Minor ◽  
Plate Reconstruction

The Matthew Creek Metamorphic Zone (MCMZ) exposes what is inferred to be the lowest structural level of the lower Aldridge Formation in the Canadian portion of the Belt–Purcell Supergroup. Zircon, monazite, and titanite were dated using the U–Pb system by LA–ICP–MS. The detrital zircon populations of quartzite layers in these rocks define a provenance dominated by sources of Laurentian affinity with a minor component of non-North American ages between 1600 and 1490 Ma. Special attention was paid to monazite in sillimanite-grade metapelitic schists that was analyzed using in situ LA–ICP–MS techniques guided by BSE imaging and compositional mapping. Textural and geochronological evidence indicate that coupled dissolution–reprecipitation affected detrital monazite at 1413 ± 10 Ma. This was followed by prograde monazite growth at 1365 ± 10 Ma, synchronous with crystallization of the nearby Hellroaring Creek peraluminous granite at 1365 ± 5 Ma. Late-stage pegmatite emplacement and ductile shearing along the contact of the MCMZ and overlying rocks occurred at 1335 ± 5 Ma, interpreted as a period of post-collisional extension, core complex formation, exhumation, and decompression melting. The entire package was subsequently affected by a pervasive ∼1050 Ma hydrothermal overprint that partially reset U–Pb dates in monazite, zircon, and titanite contained in all lithologies examined. The lowermost Belt–Purcell stratigraphy in southeast British Columbia preserves a detailed record of sedimentary provenance and a long history of episodic collision and extension that must be reconciled with plate reconstruction models for the break-up of the Nuna supercontinent and assembly of Rodinia.

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