Kurts Flin Flon Paper

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GEOLOGY 408: Geological Mapping IIMap Area 4

Kurt Soparlo, 11048283

Partner: Garett LePoure

!ate: Octo"er 8t#, 2010


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Introuction

The city of Flin Flon and surrounding region, boasts some of the most interesting

and unique geology that can be seen today. It is a region that is world renowned for its

volcanogenic massive sulfide accumulations of zinc and copper. As part of a yearly field

course at the University of as!atchewan, a study was conducted to further student"s

!nowledge on different mapping s!ills and interpreting roc! e#posures. Field e#perience

is crucial in order to fully understand the physical geology of a region. tudents were

e#posed to different pac!ages composed of metamorphosed volcanic and sedimentary

roc!s and the structures within them

$ee Figure % for e#ample&. The pro'ect

required students to use the s!ills learned

and map these formations as accurately

as possible. uch equipment as

compasses, roc! hammers and hand

lenses were found to be vital pieces in

the creation of these maps. It was also required that a roc! sample be ta!en, which would

later be cut into a thin section and further analyzed $pages %( and %%&. The ob'ective) to

determine its history and relationship to other roc!s in the region.

*arett +eoudre and I were paired together to study and map area four which

bordered several la!es and encompassed many different lava flows. Throughout the

wee!, we tre!!ed through various terrains and were e#posed to a wide range of

geological formations. -ur interpretations were based on r tauffer"s show/and tell

seminars, and from general !nowledge learned in the geology program. -ur hand lenses

$IG%&E 1: +oad cast structure0 formed from an overlyingdenser lava.


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became essential in observing grain size and identifying

different phenocrysts $Figure 1&. 2ith sharp contacts

present, being alert and aware of the geology below our

feet was crucial in creating the most accurate map

possible. The town of Flin Flon is actually incorporated in parts of our map, which made

mapping quite interesting as areas li!e a local grocery store and hoc!ey rin! became !ey

aspects when getting a bearing on our location. As *lobal ositioning ystems become

more popular with time, important mapping s!ills are being faded into e#tinction.

3owever, these s!ills are not only significant in understanding the true geology of what

once was, but instead remind us of how far we have come in creating the very maps that

we use today.

&egional Geological Setting

The ma'or mountain building event that too! place almost 1 billion years ago and

formed the largest aleoproterozoic orogenic belt in the world is !nown as the Trans/

3udson -rogen or the T3-. It was also at this time, that an ancient seaway !nown as the

4ani!ewan -cean occupied the ma'ority of the 5hurchill rovince. This belt can further

be divided into two separate zones !nown as the 5ree +a!e and the 6eindeer +a!e zone.

Furthermore, another subdivision, the Flin Flon Domain, happens to be one area of

particular interest. 3ere, we find 7 ma'or lithological types including the Amis! group

and the 4issi group, both of which were intensely studied in the 1(%( Flin Flon field

school $tauffer, %89:&.

$IG%&E 2: 4afic phenocrysts $;lac!&.


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Three Archean cratons that also should be noted ma!e up the Trans 3udson

-rogen. These are !nown as the uperior, the lave/6ae/3earne, and the as! craton. It

was the collision of these three cratons that created an orogeny that e#tends up into

northern 5anada to specific location along the nowbird Tectonic &. It should be noted that this tectonic feature runs almost ?(((!m

along the 5anadian hield in 5anada"s north. The roc!s mapped over the course of the

wee! all occur within the Flin Flon greenstone belt. This structure lies directly within the

T3-. It is because of this suture zone we see a wide variety of bac! arc and island arc

volcanics all ranging in a distinct composition, as well as plutons, and continental and

oceanic sediments $;erman, avis, = ehrsson, 1((>&. .

The roc!s of this greenstone belt represent the construction of an intra/oceanic

arc, resulting from convergence and accretion with the as! 5raton creating what is now

!nown as the elican Thrust. The elican Thrust !m and occurs where volcanic/plutonic and

sedimentary derived roc!s of Flin Flon/*lennie 5omple# were thrust over an Archean

pac!age !nown as the @an +a!e 5omple# $Ashton, +ewry, = tauffer, 1((&. The

ma'ority of these roc!s vary between basaltic to andesitic/basaltic, with more felsic

regimes often related to periods of eruption and sulfide accumulation. As a whole, these

roc!s are classified under the Amis! *roup which form the ma'or part of the greenstone

belt e#plained earlier. -ver the time period between %.98 and %.9>*a, many eruptive

episodes occurred in which these roc!s were emplaced. As time progressed, the volcanic

arcs continued to build up eventually emerging and the Amis! *roup would then become

overlain unconformablyby sandstones and conglomerates of the 4issi *roup through


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fluvial processes. 5ontinuous deformation too! place as craton/arc/craton collision

caused the roc!s of the Amis! and 4issi groups to develop a greenschist grade

metamorphism. This occurred after the boundary intrusions were input around %.:/%.9*a

$tauffer, %8>:&.

Geolog' o( Map )rea


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After mapping Area B: for the Flin Flon

4anitoba field school, we discovered a variety of

basalts0 porphyritic, massive, porphyritic

pillowed, massive pillowed and amygdaloidal

pillowed basalts $Figure ?&. The 4issi pac!age

$to the Cast& also made up a large portion of our

map, and contained its respective sandstoneDconglomerate

composition. 5ross/bedding appeared evident in parts of the

pac!age as seen in one

e#ample shown in Figure :.

pheroidal

weathering was

also present

along the

Amis!/4issi unconformity. -ther roc! types

seen were pyroclastic tuffs $Figure &, flow

breccia $Figure 7&, felsic volcanics, as well as boundary intrusions. It should be noted

that the 4issi group conglomeratesDmeta/sandstones and the mafic dy!es $i.e. Flin Flon

dy!es) Figure >& were all affected by a series of faults and shears. -ur map area

contained gabbro boundary dy!e intrusions with coarse grains as well as numerous Flin

Flon dy!e intrusions. It was common to find chilled marginsalong these particular

intrusions $Figure 9&. It would be appropriate to state that our area underwent

*reenschist metamorphism, suggesting such minerals as plagioclase, hornblende, and

$IG%&E 4: 4issi andstone showing cross/

bedding

$IG%&E 3: illow ;asalts present throughout map area.

$IG%&E *: Tuff layering present

$IG%&E +: Flow ;reccia

$IG%&E : Flin Flon y!e


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pyro#ene would not have survived. 3owever, a thin section analysis $page %%& suggests

otherwise. After confirming with rofessor an, it was found that 3ornblende does e#ist

as a relict mineral and that lagioclase $in

the form of albite& actually ma!es up the

ma'ority of the roc! as interstitial grains.

Therefore, the bul! mineral composition can

only be assumed to be) lagioclase $Albite&,

Actinolite, and 5hlorite. These minerals

help indicate a roc! that has a grade of *reenschist $e#cluding Cpidote, which could not

be identified in my particular hand sample, but surely would have been present in other

parts of the domain&. Te#tures, including a tuff/li!e

breccia $3yaloclastic&, were found in parts of the map

area. These indicate a rapid cooling rate as grain size

appeared to be aphanitic. 4y interpretation is that

they most li!ely formed in a subsea environment

where hot lava e#truded into overbearing seawater thus cooling quic!ly. The pillows

present would have also formed in a similar environment// more li!ely a shallow oceanic

arc. In our area, we had two different phenocryst compositions, thus suggesting separate

flows. 4afic and Felsic phenocrysts appeared evident in our area and can be

differentiated when loo!ing at the map $Figure %1&. These phenocrysts were quic!

indicators of different flows and also suggest a different composition of the original flow.

Felsic phenocrysts can be seen in Figure 8 and mafic phenocrysts are seen in Figure 1. A

common feature that not only assisted in recognizing a Esurface flow, but also helped to

$IG%&E 8: Intrusions containing Echilled margins.

$IG%&E -: Felsic henocrysts $white&.


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determine a Eway/up were amygdaloidal vesicles $Figure %(&. A few measurements that

should be noted include our average bedding and average cleavage. From a total of ten

stops, we found our average bedding to be (%(D1C. Ten stops also helped determine

an average cleavage of ??9D:C. ome of the measurements ta!en at these stops seem

s!ewed from the rest and possible sources of error may include a folding a event that may

have affected the bearing. G-TC) we could not identify such a feature as the erroneous

measurements were ta!en on a massive bedding pac!age.

-ur geological history of 4ap Area : is as follows)

Amis! volcanics, dated %.8 to %.99*a. These particular volcanics are composed

of tholeiitic and calc/al!aline basalts. Non-porphyritic volcanics deposited before

porphyritic volcanics.

-ur area consists of several basalt flows, all of which were previously noted.

4any flows contained vesicles which helped indicate the surface of a flow. It

was common for these flows to have a contact along a volcanic tuff or even a

felsic lava.

4ap Area : contained several ma'or flows. These include) flow breccia $Figure

%%&, massive billow basalts, porphyritic basalts, porphyritic pillow basalts,

$IG%&E 10: Amygdaloidal vesicles


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volcanic tuff $pyroclastic&, and also massive pillow basalts. Amygdaloidal pillow

basalts were also among these.

A measurement was ta!en regarding the

pillow younging direction) %(. This

was based on the cusp of the pillow.

2hen loo!ing at the map $Figure %1&,

several dy!es are seen. These dy!es

$mafic in composition& and cross cut the

volcanics.

4y personal interpretation is that the mafic dy!es aresynvolcanicand are related

to the Amis! volcanics. They are also associated with a feeder dy!e system $Flin

Flon y!es& which are related to the subsequent volcanic events.

These particular dy!es contain a grain size that is coarser than the volcanics and

contain many phenocrysts composed mostly of plagioclase and some pyro#ene.

-ur map area did not appear to have any mafic dy!e"s cross/cutting the 4issi

pac!age sandstones. Therefore, we

!now that the dy!es are older, about

%.9?*a and younger then the Amis!

volcanics $%.8*a&.

$IG%&E 11: Flow ;reccia


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The ;oundary Intrusions, shown in orange on the map, are the ne#t pac!ages to

be deposited. These intrusions were dated at %.9:1*a.

The entire pac!age was then overlain by the 4issi group appro#imately %.9:*a.

Sa.ple !e/cription

;y the last day of field school, I had collected a sample that would later be further

analyzed and studied. It was labeled as 6oc! ample B%: and was collected from a

*abbro di!e located about :(m due north from +ouis +a!e. This particular outcrop was

e#cellently e#posed but was only a small Eblip compared to many of Flin Flon"s

outcrops.

To the na!ed eye, the roc! sample has a green colored appearance and contains

dar! phenocrysts of a mafic composition. It does have some evident weathering on parts

of the roc! which gives the roc! a brownish tinge.

3owever, a clean, fresh surface displays a uniform

light green color with intermittent phenocrysts. ome

of the phenocrysts, being quite large $H?mm&, were

identified as actinolite and were present throughout.

-riginal composition would have most li!ely been

composed of minerals such as plagioclase and some

amphiboles. As mentioned, this would e#plain the

relict mineral presence of hornblende. The sample itself is about 8>cm and was

retrieved by blunt force using an Cstwing roc! hammer.

$igure 13:*abbro y!e hand specimen.

$IG%&E 12: *eological 4ap of Flin Flon0 Area :.


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A more detailed analysis was possible after attaining the thin section of the

*abbro y!e roc! sample. I determined the bul! roc! composition to be)

lagioclase $Albite&JJ..:(K ////////////$(.(%/(.%mm&

ActinoliteJJJJJJ..?(K////////////$(.1/%.(mm&

5hloriteJJJ.................1(K////////////$(.%/(.mm&

3ornblendeJJJJJ.%(K//////////////$(.1/%.(mm&

5arbonatesJJJJJJ>K/////////////$(.(%/(.>mm&

-paquesJJJ. ?K//////////////$(.%/(.mm&

$igure 14:*abbro y!e thin section.

lane olarized +ight. 4agnification) :/mm

$igure 1*:*abbro y!e thin section.

5ross olarized +ight. 4agnification) :/mm

3ornblende

3ornblende

Actinolite

Actinolite

lagioclase

lagioclase


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Te#tures present include a mesh te#ture seen in most minerals especially the

Albite. The processes of metamorphism and deformation help create this te#ture.

oi!ioblastic te#ture seen in some of the larger phenocrysts appeared evident. 4inerals

li!e hornblende and actinolite were among these that included this te#ture. Also,

minerals that were relict should also be noted. 3ornblende and lagioclase would fall

under this category. The suggested protolith would be an intrusiveboundary intrusion.

;ecause coarse grains are present, an intrusive environment is the most logical

assumption. -paques would have been the first to crystallize followed by the larger

phenocrysts $hornblende& and plagioclase. It is safe to say the Albite crystallized late in

the formation of the roc!, as the mesh te#ture is present interstitially. *reenschist

metamorphism would have altered minerals li!e pyro#ene and hornblende, into minerals

li!e actinolite and chlorite respectively. ince shistosity is non/e#istent, the most

appropriate roc! name is) actinolite/chlorite/greenstone.

&e(erence/

Ashton, L, +ewry, @, = tauffer, 4. $1((&. The pelican thrust zone) basal detachment

between the archean sas! craton and paleoproterozoic flin flon M glennie comple#,

western trans/hudson orogen. Canadian Journal of Earth Sciences, $:1&, 6etrieved fromhttp)DDrparticle.web/p.cisti.nrc.caDrparticleDAbstractTemplateervletN

caly+angOeng='ournalOc'es=volumeO:1=yearO1((=issueO:=msnoOe(:/(?

;erman, 6, avis, 2, = ehrsson, . $1((>&. 5ollisional snowbird tectonic zone

resurrected) growth of laurentia during the %.8 ga accretionary phase of the hudsonianorogeny. !eoscience "orld, #$$%(&, 6etrieved from

http)DDgeology.geoscienceworld.orgDcgiDcontentDabstractD?D%(D8%%

tauffer, 4el. %8>:. *eology of the Flin Flon area) A new loo! at the sunless city.

epartment of *eological ciences, University of as!atchewan, p. ?(/?.

tauffer, 4el. %89:. 4ani!ewan) An early roterozoic ocean in central 5anada, Its

igneous history and orogenic closure. recambrian 6esearch, 1 p. 1>/19%.

tauffer, 4el. Ehow and Tell *eology :(9. Flin Flon, 4anitoba.


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