8 resultados para Fort Rock Volcanic Field

em Brock University, Canada


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Microbial ichnofossils in volcanic rocks provide a significant record of subsurface microbes and potentially extraterrestrial biosignatures. Here, the textures, mineralogy, and geochemistry of two continental basaltic hydrovolcanic deposits - Reed Rocks and Black Hills - in the Fort Rock Volcanic Field (FRVF) are investigated. Methods include petrographic microscopy, micro and powder X-ray diffraction, SEM/BSE/EDF imaging, energy dispersive spectroscopy, stable isotopes, and X-ray fluorescence. Petrographic analysis revealed granular and tubular textures with biogenic morphologies that include terminal enlargements, septate divisions, branching forms, spiral filaments, and ovoid bodies resembling endolithic microborings described in ocean basalts. They display evidence of behaviour and a geologic context expressing their relative age and syngenicity. Differences in abiotic alteration and the abundance/morphotype assemblage of putative microborings between the sites indicate that water/rock ratio, fluid composition and flux, temperature and secondary phase formation are influences on microboring formation. This study is the first report of reputed endolithic microborings in basalts erupted in a continental lacustrine setting.

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Frank Reynolds was in charge of the Rock at Brock featuring the Guess Who and 7 other Canadian Bands, held on the back field at Brock. It was a geat affair, with 40,000 in attendance and few incidents. The student union rented every bus the City of St Catharines owned and took everyone home at 1 AM when the event ended.

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The Island Lake greenstone belt is one of the major Archean supracrustal exposures in the northwestern part of the Superior Province of the Canadian Shield. This belt is subdivided into two units: 1) a lower sequence characterised by pillowed to massive, locally pyroclastic, basalt to andesite with a thin central zone of felsic derivatives, all of which are interbedded with and overlain by thick sequences of turbidite facies rock; 2) the upper unit which consists of thick stratified conglomerate overlain by thickly bedded arkose and feldspathic greywacke. Reconnaissance sampling traverses were completed across both the strike of the belt and along its margins with adjacent granitoids. Most of the belt is within the greenschist metamorphic f acies with amphibolite facies occurring in certain areas near t he margins. A post-tectonic, low pressure thermal event may be responsible for the development of a unit of cordierite schi s t which stretches southeastwards from the east end of Cochrane Bay. Volcanism is cyclical in nature changing from tholeiitic to calc-alkaline. There is a general progression in the character of the lavas from mafic t o felsic with stratigraphic height. Chemica l d a ta sugges t that h i gh level fractionation of a mantle- derived ' dry' magma i s t he s ource of the thole i iti c lavas. Contamination of this magma with 'we t' sia l and subsequent fractionation may be r esponsi b l e for the calcalkaline phases .Observations of stratigraphic relationships (in particular the contact between the supracrustals and the granitoids) coupled with the metamorphic and chemical studies, allow the construction of a preliminary model for the evolution of the Island Lake greenstone belt. The following sequential development is suggested: 1) a platform stage characterised by the subaqueous effusion of mafic to intermediate lavas of alternating tholeiitic and calc-alkaline affinities; 2) an edifice stage marked by the eruption of felsic calc-alkaline rocks; 3) an erosional stage characterised by the deposit~on of thick sequences of turbidite facies rocks; 4) the impingement of granitic masses into the margins of the greenstone belt, which was probably related to a downward warping of the supracrustal pilei 5) the erosion of sialic massifs surrounding and within the greenstone belt and of early supracrustal piles, to give the clastic upper unit.

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The Paint Lake Deformation Zone (PLDZ), located within the Superior Province of Canada, demarcates a major structural and lithological break between the Onaman-Tashota Terrane to the north and the Beardmore-Geraldton Belt to the south. The PLDZ is an east-west trending lineament, approximately 50 km in length and up to 1 km in width, comprised of an early ductile component termed the Paint Lake Shear Zone and a late brittle component known as the Paint Lake Fault. Structures associated with PLDZ development including S-, C- and C'-fabrics, stretching lineations, slickensides, C-C' intersection lineations, Z-folds and kinkbands indicate that simple shear deformation dominated during a NW-SE compressional event. Movement along the PLDZ was in a dextral sense consisting of an early differential motion with southside- down and a later strike-slip motion. Although the locus of the PLDZ may in part be lithologically controlled, mylonitization which accompanied shear zone development is not dependent on the lithological type. Conglomerate, intermediate and mafic volcanic units exhibit similar mesoscopic and microscopic structures where transected by the PLDZ. Field mapping, supported by thin section analysis, defines five strain domains increasing in intensity of deformation from shear zone boundary to centre. A change in the dominant microstructural deformation mechanism from dislocation creep to diffusion creep is observed with increasing strain during mylonitization. C'-fabric development is temporally associated with this change. A decrease in the angular relationship between C- and C'-fabrics is observed upon attaining maximum strain intensity. Strain profiling of the PLDZ demonstrates the presence of an outer primary strain gradient which exhibits a simple profile and an inner secondary strain gradient which exhibits a more complex profile. Regionally metamorphosed lithologies of lower greenschist facies outside the PLDZ were subjected to retrograde metamorphism during deformation within the PLDZ.

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In the Elliot lake region of northern Ontario, Yolcanlc lava piles represent the lowermost units of the Huronian SUpergroup. These rocks general1y trend east-west and belong to the Elliot lake Group. They are s1tuated on the north and south limbs or the QuIrke lake Syncline. The volcanIc rocks of this study contain a secondary minerai assemblage consisting of actinolite, biotite, chlorIte, eptdote/cllnozoislte tttanomagnettte and calcite characteristic of greenschist metamorphism. Compilation of data suggests that metamorphism of the volcanic rocks proceeded between 325- and 425-C and between 2.4 and 4.7 kb. Geochemtcally these lavas represent tholeiitic and calc-alkaline assemblages. The tholeiites are character1sttcally enriched tn Fe and Tt and consist mainly of basalts, basaltic andesites and andesites. These rocks are believed to have formed by the partIal melting of a peridottte source at low P-T. In contrast, the calc-alkaline rocks are depleted in Fe and TI, but show a signIficant enrichment In 51 and Zr; andesIte Is the major rock type for thIs assemblage. I·t Is postUlated that the calc-alkalIne sU1te of rocks was the result of eIther the partIal meltIng of abasaltic·magma at shallow depth, or the melttng of s1al1c crustal materIal due to the added we1ght of tholeiitIc material on an unstable crust and to downwarplng processes Inttlated by convection cells.

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Transcript (original grammar and spelling retained): My dear wife I take this time to inform you that I am well hoping that these few lines will Reach you and find you the same I shall in form you of all our Battles that we have had sence I left home we crossed in to Canada the 2 day of July and took fort Erie on the 3 day of July without loss of one man. We then marched down to Chipway eighteen miles below the Fort Erie we got there on the forth day and had our first battle on the 5 day our loss was not jistly known But the inemy loss was double to ours. The 6 day we started with the 2 Brigade to make a bridge a crost the crick two miles a bove the fort in Building the Bridge the inemy Brought up their Canon and playd upon us with their artiliery a bout two hours We drove them from the fort our loss was none the inemy loss was nineteen ciled dead on the ground we then marched to Queenston when we got thare our inemy had fledfrom the fort we then remained thair to Queenston ten days then we marched down to Fort George But that caurdly Chaney did not a rive with the fleet so we had to return back to Queenston thare was a bout six hundred militia formed on the heights of land thay fired up on us from their pickets and retreated to the mane body our flankers ciled and wounded and took about twenty before they got to the Maine body we then marched up the hill they gave us two firs but did not damage and then retreated from the field we stayed there one knight and then marched to Chipway and stayed there one night and the next day just as the sun set the first Brigade marched up in order to give them Battle a bout two miles from the Crick and began the Battle the 2 Brigade has to March up to the Niagara path and ingaged them we charged up on their artlery and took all their Canon Miller commanded the four companys that charged....the battles lasted three hours and forty minutes our loss was about 8 hundred cild and wounded our inemies loss was a bout fourteen hundred cild and wounded the next morning we Marched up in order to give them Battle a gin but thay was afraid to ingage us we then marched to Fort Erie and went to fortiffing and made a strong place the inemy folered us up and Began to cananade and held it fifty three days thay a tacked the fort the fifteenth of august thay atacked a bout one hiour be fore day Light we saw them and Blue up our maggerzean & two hundred of our inemy our loss wasa bout forty cild and wounded and our inemy loss was a bout one thousand on the 7 Day of September we atacked them and took their batteries and Broke all their canon and drove them from the field our loss was a Bout two hundred cild and wounded our inemy loss was a Bout 8 hundred cild and wounded...we crossed in to Canada with five thousand and came out with fifteen hundred we then Marched to Sackett’s harbor....am well and harty for the present....a bout comming home it uncarting for there is not any....given this winter as yet But I shall try to Come home if I Can But if I Cant I want you should take good car of the Phiddness[?] I have not Received any Money as yet But soon as I do receive some I send some home. I want you should write to me as soon as you receive this and and how Much Stock you wintor I Received your Letter with Great pleasure I feel uneasy a bout you I am a frade that you are sick or dead this is from your husband Chase Clough

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The Introduction of the text reads: "After nearly forty-four years of silence, I consider it wise to present to the public the inner history of the Fenian Raid of 1866, where an incompetent military officer was entrusted with the lives of a small body of men, and, who by failure in the performance of a sacred duty, may prove a wholesome and useful lesson to commanders of troops in the field."