The Mount Pleasant Caldera is a large eroded

Late Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding ...

volcanic A volcano is commonly defined as a vent or fissure 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 fo ...

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

complex, located in the northern

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

of southwestern

New Brunswick New Brunswick is a Provinces and Territories of Canada, province of Canada, bordering Quebec to the north, Nova Scotia to the east, the Gulf of Saint Lawrence to the northeast, the Bay of Fundy to the southeast, and the U.S. state of Maine to ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

. It is one of few noticeable pre-

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

calderas, and its formation is associated to a period of crustal thinning that followed the

Acadian orogeny The Acadian orogeny is a long-lasting mountain building event which began in the Middle Devonian, reaching a climax in the Late Devonian. It was active for approximately 50 million years, beginning roughly around 375 million years ago (Ma), wi ...

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 during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding C ...

, and is partially covered in the north by overlying Middle Mississippian and Pennsylvanian Period

strata In geology and related fields, a stratum (: strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by v ...

. 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 (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...

turbiditic metasedimentary rocks of the local Digdeguash and Flume Ridge geological formations. Late Silurian to Devonian

granitic A granitoid is a broad term referring to a diverse group of coarse-grained igneous rocks that are widely distributed across the globe, covering a significant portion of the Earth's exposed surface and constituting a large part of the continental ...

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, 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 (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

produced by Pleasant is rich in

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

, 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 surrou ...

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 co ...

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...

, and other

igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

s rich in the mineral. Silica-rich magma does have a high

viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

, and therefore does not flow easily like

basalt Basalt (; ) is an aphanite, 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 planetary surface, surface of a terrestrial ...

. 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, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...

over wide areas. Intrusion-related

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

veins Veins () are blood vessels in the circulatory system of 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 those of the pulmonary and fetal c ...

have recently raised great interest among economic geologists. In southwestern New Brunswick, which is part of the Canadian Alleghenian orogeny, 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 has proven to be an ideal candidate.

Granitic A granitoid is a broad term referring to a diverse group of coarse-grained igneous rocks that are widely distributed across the globe, covering a significant portion of the Earth's exposed surface and constituting a large part of the continental ...

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 Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

breccia Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language ...

s and veins cut the McDougall Brook Microgranite and its volcanic wall-rock, while

molybdenum Molybdenum is a chemical element; it has Symbol (chemistry), symbol Mo (from Neo-Latin ''molybdaenum'') and atomic number 42. The name derived from Ancient Greek ', meaning lead, since its ores were confused with lead ores. Molybdenum minerals hav ...

bismuth Bismuth is a chemical element; it has 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 nat ...

tungsten Tungsten (also called wolfram) is a chemical element; it has symbol W and atomic number 74. It is a metal found naturally on Earth almost exclusively in compounds with other elements. It was identified as a distinct element in 1781 and first ...

and later polymetallic mineralization are related to the multiphase Mount Pleasant Granite. The numerous

felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...

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 u ...

. 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 volcano, volcanic object created when magma hardens within a Volcanic vent, vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if risi ...

s about apart. The volcanic necks are defined by magmatic-hydrothermal

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

(

), thick

layers, and intermediate to

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 volcanic gas, gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average ...

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 include ...

lavas,

alluvial Alluvium (, ) 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. Alluvium is also sometimes called alluvial deposit. Alluvium is ...

redbeds, and

porphyritic Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning ...

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

. 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 predomina ...

flows were probably derived from basaltic magma by the

crystallization Crystallization is a process that leads to solids with highly organized Atom, atoms or Molecule, molecules, i.e. a crystal. The ordered nature of a crystalline solid can be contrasted with amorphous solids in which atoms or molecules lack regu ...

of the magma material. The relatively rare, more

flow units, are thought to have originated from high-end crystallization inside the

. 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 The Acadian orogeny is a long-lasting mountain building event which began in the Middle Devonian, reaching a climax in the Late Devonian. It was active for approximately 50 million years, beginning roughly around 375 million years ago (Ma), wi ...

in the northern

Appalachians The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

. 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 Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more al ...

. 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 Lapilli (: lapillus) is a size classification of tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts. ''Lapilli'' is Latin for "little stones". By definition lapilli range from in diam ...

(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 extremely vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicula ...

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 pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...

. The top member consists of a

fine-grained Granularity (also called graininess) is the degree to which a material or system is composed of distinguishable pieces, "granules" or "grains" (metaphorically). It can either refer to the extent to which a larger entity is subdivided, or the ...

, typically

reddish Reddish is an area of the Metropolitan Borough of Stockport, Greater Manchester, England, south-east of Manchester city centre. At the 2011 United Kingdom census, 2011 census, the population was 28,052. Historic counties of England, Historical ...

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

texture. Calcite veins and hematite bands near the top of the layer indicate that this was a period of degassing 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 Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

laced with

calcrete Caliche () is a soil accumulation of soluble calcium carbonate at depth, where it precipitates and binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or s ...

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 rocks, which are sedimentary rocks exhibiting

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

, 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, also known as mudslide or mud flow, is a form of mass wasting involving fast-moving flow of debris and dirt that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/se ...

occurs near the top of the formation in some places. A dated locality from the top of the formation has been dated to the

, 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

composition intrudes older stratas. This layer is unique for it bridges the exocaldera and intracaldera sequences. A layer of

saprolite Saprolite is a chemically weathered rock. Saprolites form in the lower zones of soil profiles and represent deep weathering of the bedrock surface. In most outcrops, its color comes from ferric compounds. Deeply weathered profiles are widespread ...

(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

-ridden lapilli tuff section near the believed top section additionally has a 1% composition of the mineral

amphibole Amphibole ( ) is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is ...

. 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

. 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, macros ...

s and

. 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 Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

and

feldspar Feldspar ( ; sometimes spelled felspar) is 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 ''plagiocl ...

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 th ...

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

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, 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 coo ...

, 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 plagioclase ...

. The grain size of the porphyry and the size and abundance of feldspar increases inward. Amphibole with

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

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

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 In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

. 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

. 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, 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

Mount Pleasant has a long history of exploration and development in mining.

Tin Tin is a chemical element; it has symbol Sn () and atomic number 50. A silvery-colored 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, a bar of tin makes a sound, the ...

was first discovered on the mountain in 1937. The focus of exploration over the years has shifted from tin-base metals to porphyry

deposits, and then to porphyry tin deposits, and now

indium Indium is a chemical element; it has Symbol (chemistry), symbol In and atomic number 49. It is a silvery-white post-transition metal and one of the softest elements. Chemically, indium is similar to gallium and thallium, and its properties are la ...

, 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 Fredericton (; ) is the capital city of the Provinces and territories of Canada, Canadian province of New Brunswick. The city is situated in the west-central portion of the province along the Saint John River (Bay of Fundy), Saint John River, ...

, the provincial capital. The mining company Adex Mining 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 The international border between Canada and the United States is the longest in the world by total length. The boundary (including boundaries in the Great Lakes, Atlantic, and Pacific coasts) is long. The land border has two sections: Canada' ...

. 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 publish ...

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

, 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.

References

{{DEFAULTSORT:Pleasant Caldera, Mount Calderas of New Brunswick Extinct volcanoes of North America Devonian calderas Polygenetic volcanoes Landforms of Charlotte County, New Brunswick