Bancroft region

The Bancroft region of the province of Ontario is endowed with diverse geographical formations, and so has a rich history of their construction. Because the region has not undergone new metamorphic evolution since the orogeny, it is seen as a suitable area for research into Grenville and pre-Grenville era tectonics. Because much study has taken place here, the area is the source of most of the knowledge known about the orogeny. Because the area covered by the trip was suitable for the field study, a lot of information was acquired, and this report intends to provide a brief description of the material gathered during the field trip. Regional Geology and Tectonic

The region has two region of different degree of change and style of tectonic. Highland of Haliburton-Hastings is to the North whereas Hastings basin towards the South. To the west there are parallel regions of mylonitisations that stretches to the north east and southeast about three kilometers width.(Hewitt, 1956). The highland has a terrain of gneisses as well as harmonious intrusions together with a lot of granitization evidence that has destroyed the initial evidence of the initial rock deposition features. The basin is basically made up of a third of calcareous rocks and are the dominant rocks while the feldspatch is common in the in the north.Hewitt 1957. In the Central area of the region, numerousplanar huge mafic rocks are present. Fig 2. Towards the south of Lake Bay there are exposed layers of marble of pure calcite dull brown in colorandgranoblastic conglomerates of quarts composed of biotite, plagioclase and calcite traces and calc-silicate rocks are present. To the East of the lake lay huge deposits of white marble composed of calcite composed of large number of irregular quartz close to interlayered marble and calc-silicate rock though less exposed. The south of the lake there intermediate massive-weakly foliateddiopside quartz-calcitephlogopite-microcline rock. North West of bay lake is characterized by layers of therepelitic gneiss as well as schist. There are also clear lenses of as well as rods of glassy quarts and lots of muscovite that comprise this rock.

Pregrenvillian rocks Laurentian margin rocks facing the Grenville front on one side and the thrust zone of Metasedimentary belt is a representation of the Archaen crust or Paleoprotozoic as well as Mesoprotozoic rocks encroached to it or close to arcs known as Andean with exception of tectonic slices. Grenvilliandeformation, structural and metamorphism trendsis taken as the northwest Grevillian front which is exposed. Sudburrydiabase dykes are found the Grenville and the Southern Province and have been metamorphosed and deformed to the south as\east of the front of Grenville. The Grenville Laurentian margin is seen to extend into the south east of the 1450 Ma migmatiticgranitoids of Muskoka region. L2 and L3 Laurentian margin segmentrocks are made up of top mhibolite-facies and local granulite-facies

Supported by a lot of evidence like the dyke swarms and HuronianSupergroup distribution, theArchaen structure might have provided an avenue of continuous shifting at the Paleoproterozoic.The transect area, the vast Eastbull lake mafic intrusive suite resulted from the rifting of margin at about 2450 Ma and other features like the Hearst and Matachewan. An great ca. 2220 Ma continental tholeiiticmagmatism that occurred, might have been related to continental extension localized close to Sudbury region, included the deposition of gabbro suite Nipissing and into HuronianSupergroup succession.

Local Geology and Tectonic

The Southern Ontariois marked by the roots of an ancient mountain which lays mostly bare the major anomalies here do not seem to be in line with the chief faults within ca.450 m years old limestone found on top of rocks that are crystalline formed deposition of the limestone. There is also presence of the Grenville orogeny. Central gneiss belt, made up of a collection of sheets crystalline sheets stretching to about 5km by width by ca and over 20km length superimposition of each other. Bancroft region has a lot of minerals with about 90% of all minerals found on the earth’s crust including gold. Tourists are able to see the mines as there is a well-kept walking trail along the mine. Ontario also has several bedrocks and glacial deposits. There is also the Gneiss, that can be seen along highway 69 close to Parry Sound which formed by evolution of rocks exposed to extreme heat and pressure. There are tectonic rocks that are transposed gneiss of repeated parallel layers.

Synthesis

There is new evidence for seismic data of geological features found in the Grenville Province according to the results found from recent research done in the area. These unit’s stratigraphicage is not known and not easily conceivable since theareaof study is limited and due to the evident complexities of the structure andmetamorphic history. The pure and impure carbon –silicate rocks are derived from a sequence of sedimentary which are overprinted by close to is chemical regional metamorphism. When the formation of the rocks were affected by regional metamorphism which hen resulted to a metamorphic zonation from biotitearea via the garnet as well as the staurolyte-kyanite regions up to the silimanite region of the average Barovian zonal scheme under low to high temperature and moderate pressure (Gomez 2006) Marbles reveal a transformation to carbonate-silicate rocks which then turn transform into calc-silicate and silicate containing carbonate.Ultimately the carbonate disappear partially in the calc-silicate and the silicate rocks containing carbonate which then change into metapelitic and metamafic rocks.

Summary

The field study that covered Peterborough to the Bancroft region of Grenville Province provided a hands on study of the area and enriched us with a lot of knowledge and even provided an avenue to learn to revisit class concepts such as the possibility tocompel geologic evolution and tectonics as well as exhumation of lithotectonic history .Although the area of study was limited and collected data not enough to characterize whole transect, it has emerged that crustal architecture emanates originally from 980 Ma orogeny, together with theamalgamation of rocks of over 1350 Ma in the margin of Laurentianandfollowingexhumation. Sufficient evidence for the history of geologic features and occurrencesfor the rocks in the margin of Laurentianin the transect region:

Even though the transect is one of most studied section of the orogeny, there is lack of significant datain some parts of this transect region. There is inadequate documentdata on the tectonic set up of vast intrusive suites megacrystic rocks that are granitoid in nature granitoid in the whole pre-Grenvillian.

Reference

Hewitt,D. F. 1956. The Grenville region of Ontario. In The Grenville problem. Edited byJ. E. Thomson. Roy. Soc. Can. Spec. Publ. No. 1, 22

Gomez, S.I Avila, G.A (2006)Petrogenesis de lasrocascalsilocatadasqueocurrencomobandas de reaction antremarmolesrocas.