Insights into the metamorphic evolution of the Belt–Purcell basin; evidence from Lu–Hf garnet geochronology

2010 ◽  
Vol 47 (2) ◽  
pp. 161-179 ◽  
Author(s):  
N. A. Zirakparvar ◽  
J. D. Vervoort ◽  
W. McClelland ◽  
R. S. Lewis
Keyword(s):  
Metamorphic Complex ◽  
Mica Schist ◽  
Garnet Amphibolite ◽  
Metamorphic Evolution ◽  
Garnet Porphyroblasts ◽  
Core Zone ◽  
The Core ◽  
Northern Idaho

We have determined Lu–Hf garnet ages from spatially separated garnet bearing localities in northern Idaho. The Lu–Hf ages are diverse and reflect a progression of Mesoproterozoic metamorphic events. The oldest Lu–Hf garnet age determined in this study is 1463 ± 24 Ma for garnet within a kyanite schist exposed in the core-zone of the Boehls Butte metamorphic complex. A garnet schist from the Priest River complex yields a well-defined age of 1379 ± 8 Ma. A garnet–staurolite schist, a garnet–mica schist, and a gem-grade Idaho star garnet sample all from the general vicinity of Clarkia, Idaho, yield ages of 1064 ± 10, 1081 ± 20, and 1078 ± 17 Ma, respectively. A garnet amphibolite, also collected from the Boehls Butte metamorphic complex, yields an age of 1151 ± 41 Ma for garnet porphyroblasts and 137 ± 25 Ma for diffuse overgrowths. The Hf in all of the Proterozoic garnets is extraordinarily radiogenic with εHf values ranging from +1210 to +10546, which attest to both their high Lu/Hf ratios and their great antiquity. All of the samples analyzed in this study are from the rocks of the Mesoproterozoic Belt–Purcell Supergroup or its basement. These data provide evidence of polymetamorphism in northwestern Laurentia during the Mesoproterozoic.

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.

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©

scholarly journals Metamorphic Evolution and Tectonic Implications of Garnet-Bearing Mica Schist in Sumdo High Pressure Belt from Eastern Lhasa Block, Tibet

2015 ◽  
Vol 89 (s2) ◽  
pp. 3-4 ◽  
Author(s):  
Mei CHEN ◽  
Jingsui YANG ◽  
Cong ZHANG ◽  
Zuolin TIAN ◽  
Jie HUANG ◽  
...  
Keyword(s):  
High Pressure ◽  
Mica Schist ◽  
Metamorphic Evolution ◽  
Tectonic Implications

U–Pb geochronological constraints for Paleoproterozoic evolution of the Core Zone, southeastern Churchill Province, northeastern Laurentia

2000 ◽  
Vol 103 (1-2) ◽  
pp. 31-54 ◽  
Author(s):  
Donald T. James ◽  
Greg R. Dunning
Keyword(s):  
Core Zone ◽  
The Core ◽  
Geochronological Constraints

Gneissic Alkalic Rocks and Carbonatites in the Frenchman's Cap Gneiss Dome, Shuswap Complex, British Columbia

1974 ◽  
Vol 11 (2) ◽  
pp. 304-318 ◽  
Author(s):  
W. J. McMillan ◽  
J. M. Moore Jr.
Keyword(s):  
Regional Metamorphism ◽  
Lava Flows ◽  
High Grade ◽  
Metamorphic Complex ◽  
Sedimentary Deposits ◽  
Gneiss Domes ◽  
The Core ◽  
Igneous Origin ◽  
Eastern Border ◽  
Shuswap Metamorphic Complex

Frenchman's Cap dome is one of a series of gneiss domes along the eastern border of the high-grade Shuswap metamorphic complex. The granitic gneisses which compose the core of the dome are enclosed in an envelope of metasedimentary rocks.Before Shuswap metamorphism and deformation, the rocks of the sedimentary envelope were intruded by concordant bodies of alkalic rocks and carbonatite. Other carbonatite bodies appear to have formed at or extruded onto the surface. It is not certain whether these are exhalative sedimentary deposits, lava flows, or pyroclastic deposits.Criteria which can be used to distinguish igneous alkalic rocks from those of metasomatic origin were almost entirely destroyed by regional metamorphism. A few relict igneous textures show that at least some of the alkalic gneisses are of igneous origin.

Geophysical characteristics of the continental crust along the Lithoprobe Eastern Canadian Shield Onshore–Offshore Transect (ECSOOT): a review

2002 ◽  
Vol 39 (5) ◽  
pp. 569-587 ◽  
Author(s):  
Jeremy Hall ◽  
Keith E Louden ◽  
Thomas Funck ◽  
Sharon Deemer
Keyword(s):  
Normal Incidence ◽  
Shear Zones ◽  
Canadian Shield ◽  
P Wave ◽  
Seismic Profiles ◽  
Grenville Province ◽  
Core Zone ◽  
The Core ◽  
Geodynamic Processes ◽  
Archean Crust

The Eastern Canadian Shield Onshore–Offshore Transect (ECSOOT) of the Lithoprobe program included 1200 km of normal-incidence seismic profiles and seven wide-angle seismic profiles across Archean and Proterozoic rocks of Labrador, northern Quebec, and the surrounding marine areas. Archean crust is 33–44 km thick. P-wave velocity increases downwards from 6.0 to 6.9 km/s. There is moderate crustal reflectivity, but the reflection Moho is unclear. Archean crust that stabilized in the Proterozoic is similar except for greater reflectivity and a well-defined Moho. Proterozoic crust has similar or greater thickness, variable lower crustal velocities, and strong crustal reflectivity. Geodynamic processes of Paleoproterozoic growth of the Canadian Shield are similar to those observed in modern collisional orogens. The suturing of the Archean Core Zone and Superior provinces involved whole-crustal shearing (top to west) in the Core Zone, linked to thin-skinned deformation in the New Quebec Orogen. The Torngat Orogen sutures the Nain Province to the Core Zone and reveals a crustal root, in which Moho descends to 55 km. It formed by transpression and survived because of the lack of postorogenic heating. Accretion of the Makkovik Province to the Nain Province involves delamination at the Moho and distributed strain in the juvenile arcs. Delamination within the lower crust characterizes the accretion of Labradorian crust in the southeastern Grenville Province. Thinning of the crust northwards across the Grenville Front is accentuated by Mesozoic extension that reactivates Proterozoic shear zones. The intrusion of the Mesoproterozoic Nain Plutonic Suite is attributed to a mantle plume ponding at the base of the crust.

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