| Title | Petrology of explosive Middle-Upper Triassic ultramafic rocks in the Mess Creek area, northern Stikine terrane |
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| Author | Milidragovic, D ;
Joyce, N L; Zagorevski, A; Chapman, J B |
| Source | British Columbia Ministry of Energy and Mines, British Columbia Geological Survey Paper 2016-1, 2016 p. 95-111  Open Access |
| Links | Online - En ligne
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| Image |  |
| Year | 2016 |
| Alt Series | Earth Sciences Sector, Contribution Series 20150348 |
| Publisher | British Columbia Ministry of Energy and Mines |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | British Columbia |
| NTS | 104G/02; 104G/03; 104G/06; 104G/07 |
| Area | Mess Creek; Shaft Creek |
| Lat/Long WENS | -131.3333 -130.7500 57.5000 57.1667 |
| Subjects | igneous and metamorphic petrology; geochronology; igneous petrology; ultramafic rocks; facies; facies analyses; pyroclastics; argon argon dates; Stikine terrane; Stuhini Group; Stikinia; Mesozoic;
Triassic |
| Illustrations | location maps; stratigraphic sections; photographs; photomicrographs; tables; plots |
| Program | GEM2: Geo-mapping for Energy and Minerals Western Cordillera, Regional porphyry transitions |
| Released | 2016 01 01 |
| Abstract | The Mess Lake facies of the Stuhini Group (Middle to Upper Triassic) in northwestern British Columbia includes a unit of pervasively serpentinized, olivine-rich, subaqueous lapilli breccia, lapilli
tuff, and ash tuff. Relatively high whole-rock MgO concentrations (29-38 wt.%; loss on ignition-free) of pyroclastic samples from this unit refl ect signifi cant accumulation of olivine. These ultramafi c pyroclastic rocks also exhibit strong
enrichment in Ba and depletion in Nb+Ta relative to La, consistent with derivation from slab-metasomatized mantle asthenosphere in a volcanic arc setting. The restored parental liquid is a primitive, mantle-derived, arc magma that contained up to
16-20 wt.% MgO. The unit contains fresh volcanic glass indicating low-grade regional metamorphism, and suggesting that it postdates emplacement of the nearby Hickman pluton, which yielded 40Ar/39Ar hornblende ages of 222.2 ±2.8 Ma, 221.6 ±2.5 Ma, and
220.1 ±2.7 Ma. The Alaskan-type ultramafi c plutons of the Polaris suite (Middle to Late Triassic) and a post-Hickman basaltic diatreme, containing picritic fragments, are spatially associated and broadly coeval with the ultramafi c pyroclastic rocks
of the Mess Lake facies, but a petrogenetic link has yet to be established. |
| Summary | (Plain Language Summary, not published)
This report presents preliminary results and models developed through GEM2 program on volcanic and plutonic rocks in British Columbia and Yukon. It
details the distribution and characteristics of rare volcanic rocks on the basis of field and laboratory analyses. It presents a new model for the origin of these rocks that requires unusual temperatures. The results presented herein help progress
GEM2 model to ultimately redefine the regional tectonic models of the Cordillera. |
| GEOSCAN ID | 297423 |
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