Ninety million years of orogenesis, 250 million years of quiescence and further orogenesis with no change in PT : significance for the role of deformation in porphyroblast growth
In situ dating of monazite grains preserved as inclusions within foliations defining FIAs (foliation inflection/intersection axes preserved within porphyroblasts) contained within garnet, staurolite, andalusite and cordierite porphyroblasts provides a chronology of ages that matches the FIA successi...
| Main Authors: | , |
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| Format: | Journal Article |
| Language: | English |
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2014
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| Online Access: | https://hdl.handle.net/10356/106125 http://hdl.handle.net/10220/23972 |
| _version_ | 1826124054271098880 |
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| author | Shah, A. A Bell, T. H |
| author_facet | Shah, A. A Bell, T. H |
| author_sort | Shah, A. A |
| collection | NTU |
| description | In situ dating of monazite grains preserved as inclusions within foliations defining FIAs (foliation inflection/intersection axes preserved within porphyroblasts) contained within garnet, staurolite, andalusite and cordierite porphyroblasts provides a chronology of ages that matches the FIA succession for the Big Thompson region of the northern Colorado Rocky Mountains. FIA sets 1, 2 and 3 trending NE–SW, E–W and SE–NW were formed at 1760.5 ± 9.7, 1719.7 ± 6.4 and 1674 ± 11 Ma, respectively. For three samples where garnet first grew during just one of each of these FIAs, the intersection of Ca, Mg, and Fe isopleths in their cores indicate that these rocks never got above 4 kbars throughout the Colorado Orogeny. Furthermore, they remained around approximately the same depth for ~250 million years to the onset of the younger Berthoud Orogeny at 1415 ± 16 Ma when the pressure decreased slightly as porphyroblasts formed with inclusion trails preserving FIA set 4 trending NNE–SSW. No porphyroblast growth occurred during the intervening ~250 million years of quiescence, even though the PT did not change over this period. This confirms microstructural evidence gathered over the past 25 years that crenulation deformation at the scale of a porphyroblast is required for reactions to re-initiate and enable further growth. |
| first_indexed | 2024-10-01T06:14:23Z |
| format | Journal Article |
| id | ntu-10356/106125 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T06:14:23Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | ntu-10356/1061252020-09-26T21:32:51Z Ninety million years of orogenesis, 250 million years of quiescence and further orogenesis with no change in PT : significance for the role of deformation in porphyroblast growth Shah, A. A Bell, T. H DRNTU::Science::Astronomy::Stellar systems In situ dating of monazite grains preserved as inclusions within foliations defining FIAs (foliation inflection/intersection axes preserved within porphyroblasts) contained within garnet, staurolite, andalusite and cordierite porphyroblasts provides a chronology of ages that matches the FIA succession for the Big Thompson region of the northern Colorado Rocky Mountains. FIA sets 1, 2 and 3 trending NE–SW, E–W and SE–NW were formed at 1760.5 ± 9.7, 1719.7 ± 6.4 and 1674 ± 11 Ma, respectively. For three samples where garnet first grew during just one of each of these FIAs, the intersection of Ca, Mg, and Fe isopleths in their cores indicate that these rocks never got above 4 kbars throughout the Colorado Orogeny. Furthermore, they remained around approximately the same depth for ~250 million years to the onset of the younger Berthoud Orogeny at 1415 ± 16 Ma when the pressure decreased slightly as porphyroblasts formed with inclusion trails preserving FIA set 4 trending NNE–SSW. No porphyroblast growth occurred during the intervening ~250 million years of quiescence, even though the PT did not change over this period. This confirms microstructural evidence gathered over the past 25 years that crenulation deformation at the scale of a porphyroblast is required for reactions to re-initiate and enable further growth. Published version 2014-10-09T01:13:43Z 2019-12-06T22:05:04Z 2014-10-09T01:13:43Z 2019-12-06T22:05:04Z 2012 2012 Journal Article Shah, A. A., & Bell, T. H. (2012). Ninety million years of orogenesis, 250 million years of quiescence and further orogenesis with no change in PT : significance for the role of deformation in porphyroblast growth. Journal of earth system science, 121(6), 1365-1399. 0253-4126 https://hdl.handle.net/10356/106125 http://hdl.handle.net/10220/23972 10.1007/s12040-012-0241-3 en Journal of earth system science © 2012 Indian Academy of Sciences. This paper was published in Journal of Earth System Science and is made available as an electronic reprint (preprint) with permission of Indian Academy of Sciences. The paper can be found at the following official DOI: http://dx.doi.org/10.1007/s12040-012-0241-3. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law. application/pdf |
| spellingShingle | DRNTU::Science::Astronomy::Stellar systems Shah, A. A Bell, T. H Ninety million years of orogenesis, 250 million years of quiescence and further orogenesis with no change in PT : significance for the role of deformation in porphyroblast growth |
| title | Ninety million years of orogenesis, 250 million years of quiescence and further orogenesis with no change in PT : significance for the role of deformation in porphyroblast growth |
| title_full | Ninety million years of orogenesis, 250 million years of quiescence and further orogenesis with no change in PT : significance for the role of deformation in porphyroblast growth |
| title_fullStr | Ninety million years of orogenesis, 250 million years of quiescence and further orogenesis with no change in PT : significance for the role of deformation in porphyroblast growth |
| title_full_unstemmed | Ninety million years of orogenesis, 250 million years of quiescence and further orogenesis with no change in PT : significance for the role of deformation in porphyroblast growth |
| title_short | Ninety million years of orogenesis, 250 million years of quiescence and further orogenesis with no change in PT : significance for the role of deformation in porphyroblast growth |
| title_sort | ninety million years of orogenesis 250 million years of quiescence and further orogenesis with no change in pt significance for the role of deformation in porphyroblast growth |
| topic | DRNTU::Science::Astronomy::Stellar systems |
| url | https://hdl.handle.net/10356/106125 http://hdl.handle.net/10220/23972 |
| work_keys_str_mv | AT shahaa ninetymillionyearsoforogenesis250millionyearsofquiescenceandfurtherorogenesiswithnochangeinptsignificancefortheroleofdeformationinporphyroblastgrowth AT bellth ninetymillionyearsoforogenesis250millionyearsofquiescenceandfurtherorogenesiswithnochangeinptsignificancefortheroleofdeformationinporphyroblastgrowth |