The Mount Pleasant Caldera is a large eroded
Late Devonian volcanic
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates a ...
caldera
A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...
complex, located in the northern
Appalachian Mountains
The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...
of southwestern
New Brunswick
New Brunswick (french: Nouveau-Brunswick, , locally ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. It is the only province with both English and ...
,
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
. It is one of few noticeable pre-
Cenozoic calderas, and its formation is associated to a period of
crustal thinning that followed the
Acadian orogeny in the northern Appalachian Mountains.
It sits relatively near to the coastline.
Geology
The large elliptical feature is dated back to the late
Devonian Period
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, w ...
, and is partially covered in the north by overlying
Middle Mississippian and
Pennsylvanian Period
strata.
The volcano is north-south trending in its elliptical shape, with minimum dimensions of as outlined by regional gravitational and magnetic studies. The northern half of the volcano has since been covered by depositional rock strata.
The caldera is bounded to the east and west by fused
Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya.
T ...
to
Silurian turbiditic metasedimentary
In geology, metasedimentary rock is a type of metamorphic rock. Such a rock was first formed through the deposition and solidification of sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and e ...
rocks of the local Digdeguash and Flume Ridge geological formations.
Late Silurian to Devonian
granitic
A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz- ...
rocks of the Saint George Batholith bound part of the southern margin of the caldera. Rocks within the summit itself date back to the
Upper Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wher ...
, and show multiple fill sequences late in its history.
The
magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...
produced by Pleasant is rich in
silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
, as indicated by a large amounts of
ignimbrite
Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surro ...
,
tuff
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...
,
rhyolite, and other
igneous rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...
s rich in the mineral. Silica-rich magma does have a high
viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inte ...
, and therefore does not flow easily like
basalt
Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...
. As a result, gases tend to become trapped at high pressure within the magma. When the magma approaches the surface of the Earth the rapid off-loading of overlying material causes the trapped gases to decompress rapidly triggering explosive destruction of the magma and spreading
volcanic ash
Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer ...
over wide areas.
Intrusion-related
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile me ...
veins
Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...
have recently raised great interest among
economic geologists. In southwestern New Brunswick, which is part of the Canadian
Alleghenian orogeny
The Alleghanian orogeny or Appalachian orogeny is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains. The term and spelling Alleghany orogeny was originally proposed by H.P. Woodward in 195 ...
, several gold deposits have been recorded in the past. The positive early results have created great interest for gold-finding efforts, and the
Mount Meager massif
The Mount Meager massif is a group of volcanic peaks in the of the Coast Mountains in southwestern British Columbia, Canada. Part of the Cascade Volcanic Arc of western North America, it is located north of Vancouver at the northern end of the P ...
has proven to be an ideal candidate.
Granitic
A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz- ...
intrusions within the caldera complex include the McDougall Brook Microgranite and the somewhat younger Mount Pleasant Granite. Gold
quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...
breccia
Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix.
The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of ...
s and veins cut the McDougall Brook Microgranite and its volcanic wall-rock, while
molybdenum-
bismuth
Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...
-
tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isol ...
and later
polymetal
In chemistry or mining, polymetal or polymetallic is a substance composed of a combination of different metals. When the substance contains only two metals the term ''bimetal'' (''bimetallic'') is sometimes preferred. A (or ') is an ore that i ...
lic
mineralization are related to the multiphase Mount Pleasant Granite.
The numerous
felsic sections are associated with episodes of
fractional crystallization in a high-level, zoned
magma chamber
A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it up ...
. Fractionation was continually interrupted by eruption of material from the roof zone such that seven phases of caldera growth have been recognized.
Mount Pleasant lies along the southwestern margin of the caldera complex. Two mineralized zones, termed the Fire Tower Zone and the North Zone, occur within
volcanic plug
A volcanic plug, also called a volcanic neck or lava neck, is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if rising volatile-charged ma ...
s about apart. The volcanic necks are defined by magmatic-hydrothermal
breccia
Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix.
The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of ...
s.
Eruptive history
The eruptive history of the Mount Pleasant Caldera can be divided into three stages of activity: the exocaldera sequence, the intracaldera sequence, and the late caldera-fill sequence. These can further be subdivided into strata based on their depth below the surrounding rock.
The Intercaldera Sequence comprises formations that crop out from overlying flows in triangularly shaped area, and includes thick
volcanic ash
Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer ...
(
tuff
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...
), thick
breccia
Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix.
The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of ...
layers, and intermediate to
felsic igneous rocks that tend to
intrude the above layers and are typically located along caldera margin faults.
The Exocaldera Sequence contains
ash flow
A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...
tuffs,
mafic
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks incl ...
lavas,
alluvial
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. All ...
redbed
Red beds (or redbeds) are sedimentary rocks, typically consisting of sandstone, siltstone, and shale, that are predominantly red in color due to the presence of ferric oxides. Frequently, these red-colored sedimentary strata locally contain th ...
s, and
porphyritic felsic lavas that are distributed across five different layers. The late Caldera-Fill Sequence contains rocks that are similar to those of the outflows of the other, older layers, and comprises two formations and two relatively minor intrusive lava flows. The volcanic flows are generally
mafic
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks incl ...
. The stratigraphic subdivision is supported by geochemical and mineralogical analyses, which indicate that the basaltic rocks are
mantle-derived and have, unusually, relatively intraplate (or
hotspot) type chemical affinities.
The multiple
andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predo ...
flows were probably derived from basaltic magma by the
crystallization of the magma material. The relatively rare, more
felsic flow units, are thought to have originated from high-end crystallization inside the
magma chamber
A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it up ...
. The various stages of fractionation are continually interrupted by eruptions, and have allowed scientists to recognize seven stages of caldera development. The genesis of the caldera is related to a period of lithospheric thinning that followed the
Acadian Orogeny in the northern
Appalachians
The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...
.
The relative position of the Exocaldera and Intracaldera sequences is based on several observations:
* The upper part of the Rothea formation (Exocaldera) contains about 1%
biotite. The only intracaldera rocks with this much biotite is volcanic strata within sedimentary breccia of and a tuff unit near the Scoullar Mountain formation (Intracaldera).
*
Andesitic strata occurs only in two flow units: the South Oromocto Andesite of the Exocaldera sequence, and the Scoullar Mountain formation of the Intracaldera sequence.
* The exocaldera Carrow formation contains clasts from the intracaldera Seelys formation.
* The exocaldera Bailey Rock Rhyolite
intrudes and overlies the Carrow formation, but is intruded by the intracaldera McDougall Brook Granite formation.
Exocaldera sequence
The exocaldera sequence consists of, in ascending stratigraphic order, the Hoyt Station Basalt, Rothea Formation, South Oromocto Andesite, Carrow Formation and Bailey Rock Rhyolite. The first and last flow units have the least extent, evidence of erosional activity after their formation but before the next deposited layer.
The first and oldest layer is the Hoyt Station basalt formation, which is composed of at least two flow units. There are two types of rock associated with the basalt,
conglomerate ranging in particle size from small pebbles to cobbles, and
lithic lapilli-
tuff
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...
(well-worn, consolidated volcanic ash).
It is only directly exposed at the surface in one area, as a tuff on an extended solidified multi-age lava flow that extends northeast from the northern section of the volcano, colored green in the diagram at right.
The next oldest layer is the Rothea formation. It can be divided into three major lava flow layers. The lower member consists mainly of unwelded (unjoined), but heavily compacted,
pumice
Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular v ...
ous lapilli-tuff and crystal tuff strata. The middle member consists of rock ranging from nearly
aphyric tuff at the base to crystal tuff near the top.
The top section of the middle unit contains
pyroxene. The top member consists of a
fine-grained
Granularity (also called graininess), the condition of existing in granules or grains, refers to the extent to which a material or system is composed of distinguishable pieces. It can either refer to the extent to which a larger entity is sub ...
, typically
reddish
Reddish is an area in Metropolitan Borough of Stockport, Greater Manchester, England. south-east of Manchester city centre. At the 2011 Census, the population was 28,052. Historically part of Lancashire, Reddish grew rapidly in the Industria ...
lava flow and another lithic tuff unit. It can be found exposed in a limited region, encompassing the flank of the Hoyt Station basalt, colored light yellow in the diagram at right; it also peeks out closer to the volcano twice.
The next layer, the South Oromocto Andesite formation, is composed of at least three flow units, with basalt flows being the most extensive. Only one exhibits a
porphyritic texture.
Calcite veins and
hematite bands near the top of the layer indicate that this was a period of
degassing
Degassing, also known as degasification, is the removal of dissolved gases from liquids, especially water or aqueous solutions. There are numerous methods for removing gases from liquids.
Gases are removed for various reasons. Chemists remove ga ...
in the flow.
It forms a thin band around the Rothea formation.
The Carrow formation is a predominantly fine-grained redbed (consisting of typically red sedimentary rocks) unit that has a grade ranging from pebbles and cobble in
conglomerate at the base to
mudstone laced with
calcrete at the top. The flow is littered with abundant flows from the Seelys (in the intercaldera sequence) and Rothea (earlier) formation towards the southeast, but in the north
metasedimentary
In geology, metasedimentary rock is a type of metamorphic rock. Such a rock was first formed through the deposition and solidification of sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and e ...
rocks, which are sedimentary rocks exhibiting
metamorphosis, predominate.
The lower part of the formation consists of unwelded and highly compacted lapilli tuff with abundant amounts of pumice fragments. A basalt and basalt-clad
mudflow
A mudflow or mud flow is a form of mass wasting involving fast-moving flow of debris that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/second. Mudflows contain a significa ...
occurs near the top of the formation in some places. A dated locality from the top of the formation has been dated to the
Late Devonian, around 350 million years ago. The exposed part of the formation forms a long band around the South Oromocto Andesite formation, and is colored brown on the map.
The last formation in the later, the Bailey Rock Rhyolite formation, is composed of
porphyritic lava, and is characterized by an absence of angular crystals and pumice derivatives. In places its
rhyolite composition
intrudes older stratas. This layer is unique for it bridges the exocaldera and intracaldera sequences. A layer of
saprolite (chemically weathered rock) separates the Bailey Rock Rhyolite formation from the overlying Caldera-Fill Sequence-era rocks. The exposed part of the flow overlies part of the Carrow formation, and is colored pink in the diagram above-right.
Intracaldera sequence
The Intercaldera Sequence is divided into, in ascending order, the Scoullar Mountain formation, Little Mount Pleasant formation, Seelys formation, and McDougall Brook Granite formation. In addition, there are felsic
dykes and one mafic dyke that intrude the Scoullar Mountain and Little Mount Pleasant formations, respectively.
The first sequence in the order is the Scoullar Mountain formation. The layer is characterized by sedimentary breccia and interbedded andesitic lava. In addition felsic
pyroclastic rocks are very common in places and one sandstone-conglomerate lava flow can be found.
The sedimentary breccia is dominated by pebble to boulder size angular metasedimentary stratas, and a few crystal tuff layers that contain about 1% biotite, the only such high amount of a typically trace mineral outside of Rothea formation in the Extracaldera sequence. A
pumice
Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular v ...
-ridden lapilli-tuff section near the believed top section additionally has a 1% composition of the mineral
amphibole. The exposed portion of the flows loosely flank the slopes of the volcano on the left and right, and are represented by bright orange on the map.
The next layer is the Little Mount Pleasant formation, which is composed of crystal tuff and banded
rhyolite. The tuff is characterized by, recrystallized pumice with microscopic
crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
s and
amphibole. The crystal structure inside the pumice are larger than those outside, indicating that significant mechanical breakage during the eruption in which they were deposited. The exposed part of this layer is located around the southern base of the main caldera, and is colored ochre (light orange) on the diagram.
The Seelys formation, next in the order, consists of lithic tuff and pumice-littered lithic lapilli-tuffs, banded, pumiceous, crystal tuff, and densely welded crystal tuff. The basalt contains clasts of both the Scoullar Mountain andesite and Little Mount Pleasant formation.
Quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...
and
feldspar
Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) felds ...
increase in size and abundance yoward the top. Biotite is virtually absent, but
zircon
Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of t ...
is very common. The formation is colored the lightest orange on the map, and swathes across the main body of the caldera.
The McDougall Brook Granite formation consists mostly of
porphyritic granite
Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...
, a borderline feldspar (sometimes quartz)
porphyry, and minor amounts of fine-grained
quartz monzonite
Quartz monzonite is an intrusive, felsic, igneous rock that has an approximately equal proportion of orthoclase and plagioclase feldspars. It is typically a light colored phaneritic (coarse-grained) to porphyritic granitic rock. The plagiocl ...
. The grain size of the porphyry and the size and abundance of feldspar increases inward. Amphibole with
apatite is the main mineral phase in all three of the flows. Parts of the feldspar porphyry are hydrothermally altered. The deposit is extensively exposed, and is colored red on the map.
Late Caldera-fill sequence
The Late Caldera-Fill sequence includes the Mount Pleasant Porphyry, the Big Scott Mountain formation, and the Kleef formation. The ages of the rocks are not well-established, but they are most likely
Late Devonian and
Mississippian. In addition the Intracaldera sequence is cut into multiple intrusions of varying origins. Many of the intrusions are thought to have formed without eruption, when mineral deposits "leaked."
The Mount Pleasant Porphyry formation occurs as dykes and small rock areas that have been associated with local breccia. The dyke structures seem to indicate multiple periods of
intrusion. Two types of breccias have been identified, and older and more common felsic series, and a younger neutral phase. The porphyries making up the rocks were emplaced at the pre-existing volcanic margin.
The Big Scott Mountain formation consists of rhyolite of variable composition, lapilli-tuff, and crystal tuff. Most of the rhyolites are characterized by large amounts of
pyroxene. One rhyolite unit appears to overlie the McDougall Brook Granite formation. The tuff is littered by clasts from the Seelys and McDougall Brook Granite formations. The tuff also appears to be layered. It is colored dark orange on the map, and the exposed part partially rings the north of the volcano.
The final formation, the Kleef formation, includes
redbed
Red beds (or redbeds) are sedimentary rocks, typically consisting of sandstone, siltstone, and shale, that are predominantly red in color due to the presence of ferric oxides. Frequently, these red-colored sedimentary strata locally contain th ...
, basalt and pumice-ridden tuff. Pebble to cobble sized conglomerate is also seen complementing the volcanic rock, and parts seem to come from older formations. The basalt is characterized by large crystals (up to ). The tuff are characterized by their reddish-brown color and abundant fossil-pumice. The formation is very rare exposed and of interest to
economic geologists, as it contains many of the possibly gold-bearing intrusive areas. It is colored light blue on the map.
Mining
![Indium wire](https://upload.wikimedia.org/wikipedia/commons/c/cd/Indium_wire.jpg)
Mount Pleasant has a long history of exploration and development in mining.
Tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
was first discovered on the mountain in 1937. The focus of exploration over the years has shifted from tin-base metals to porphyry
tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isol ...
-
molybdenum-
bismuth
Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...
deposits, and then to porphyry tin deposits, and now
indium
Indium is a chemical element with the symbol In and atomic number 49. Indium is the softest metal that is not an alkali metal. It is a silvery-white metal that resembles tin in appearance. It is a post-transition metal that makes up 0.21 parts ...
, a rare element that is important to new technologies such as LCD screens and solar cells, computers and smart phones.
The Mount Pleasant mine is located south of
Fredericton, the provincial capital. The mining company
Adex Mining
Adex Mining Inc. is a Toronto, Ontario, Canada-based mining exploration company engaged in the development of its wholly owned Mount Pleasant Mine property in Charlotte County, New Brunswick, Canada. According to a Government of Canada report, Moun ...
Inc. holds 102 prospective claims covering approximately 1,600 hectares (4,000 acres) and 405 hectares (1,000 acres) of surface rights at Mount Pleasant, dominating the local extraction rights.
It is situate close to infrastructure and potential employees. With a population of 50,000, Fredericton is important to the mine, as is
Saint John, with a population of 70,000, which lies about o the southeast. Mount Pleasant is also only from the
Canada–United States border. When the mine was last producing - 1983 to 1985 -
tungsten ore was regularly transported through Saint John by means of a provincial highway for shipment to Europe. The mine site is accessible via all-weather roads from Fredericton, Saint John and St. George. Electricity is provided by the New Brunswick transmission grid and water from a pump house located on the nearby
Piskahegan River.
On September 25, 2005, the
Society of Economic Geologists
The Society of Economic Geologists (SEG) is a scientific organization that promotes the study of geology as it relates to mining, mineral exploration, mineral resource classification and mineral extraction. The society's Publication Board publishe ...
hosted a small field trip to the caldera and the nearby Mount Pleasant Mine and Clarence stream deposit.
The trip was divided into three stages: the Mount Pleasant Caldera, the Mount Pleasant Mine, and the Clarence Stream deposits. The field crew described two trenches that seemed to outline the relationship between the volcanic rock and the possibly gold-rich intrusive areas.
On June 25, 2008, Geodex Minerals Ltd., a gold
venture firm, announced the results of a 2007 - early 2008 diamond drilling program on the west side of Mount Pleasant. Along with the development of the
Sisson Brook tungsten-molybdenum-copper project north of
Fredericton, the area surrounding the former Mount Pleasant mine has been a major focus of the company.
Research is ongoing, and focuses on the two most likely candidates: the McDougall Brook Granitic suite (MBG) and the Mount Pleasant Granitic suite (MPG).
In June 2011, the owners moved their corporate offices from Toronto to Fredericton with the intent of refocusing efforts onto getting the mine running again by 2012.
See also
*
List of volcanoes in Canada
*
Volcanology of Eastern Canada
References
{{DEFAULTSORT:Pleasant Caldera, Mount
Calderas of New Brunswick
Extinct volcanoes
Devonian calderas
Polygenetic volcanoes
Landforms of Charlotte County, New Brunswick