The Capricorn Assemblage is a geological formation comprising the central portion of the Mount Meager

Mount Meager

Mount Meager, originally known as Meager Mountain, is a complex volcano in the Sea-to-Sky Corridor of southwestern British Columbia, Canada. It is located north of Vancouver at the northern end of the Pemberton Valley. Part of the Cascade Volcanic Arc of western North America, its summit is above...

 massif

Massif

In geology, a massif is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole...

 in southwestern British Columbia

British Columbia

British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. It is named after Capricorn Mountain

Capricorn Mountain

Capricorn Mountain is one of the several volcanic peaks of the Mount Meager massif in southwestern British Columbia, Canada. The slopes of Capricorn Mountain appear to be more gentle than other volcanic peaks of the massif...

, the third highest subsidiary peak of Meager. The assemblage was formed during a period of volcanic activity about or less than 90,000 years ago.

Weathered rhyodacite

Rhyodacite

Rhyodacite is an extrusive volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of granodiorite. Phenocrysts of sodium rich plagioclase, sanidine, quartz, and biotite or hornblende are typically set in an aphanitic to glassy light to intermediate...

 is main volcanic rock

Volcanic rock

Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...

 of the Capricorn Assemblage. It forms the final of Capricorn Mountain and Mount Job

Mount Job

Mount Job is one of the six named volcanic peaks of Mount Meager in British Columbia, Canada. It is a pile of rubble held together by volcanic ash and sand...

. The rhyodacite is characterized by phenocryst

Phenocryst

thumb|right|300px|[[Granite]]s often have large [[feldspar|feldspatic]] phenocrysts. This granite, from the [[Switzerland|Swiss]] side of the [[Mont Blanc]] massif, has large white [[plagioclase]] phenocrysts, [[triclinic]] [[mineral]]s that give [[trapezium|trapezoid]] shapes when cut through)...

s of plagioclase

Plagioclase

Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...

, quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

 and biotite

Biotite

Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...

. Capricorn Assemblage rhyodacite underlies Plinth Assemblage

Plinth Assemblage

The Plinth Assemblage, also known as the Plinth Formation, is an accreted terrane of igneous rocks in southwestern British Columbia, Canada, located just north of the Lillooet River and on the northern flank of the Mount Meager massif...

 rhyodacite on the south flank of Plinth Peak

Plinth Peak

Plinth Peak, sometimes called Plinth Mountain, is the highest satellite cone of Mount Meager, and one of four overlapping volcanic cones which together form the northernmost volcanic complex in the Cascade Volcanic Arc and the Garibaldi Volcanic Belt...

.

See also

• Mosaic Assemblage
  Mosaic Assemblage
  The Mosaic Assemblage is a rock unit of the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada. It is the namesake of Mosaic Glacier, which is drained by Mosaic Creek. This geological formation formed 140,000 to less than 90,000 years ago when porphyritic...
  
  
• Job Assemblage
  Job Assemblage
  The Job Assemblage is a geological formation comprising a portion of the Mount Meager massif in southwestern British Columbia, Canada. It is named after Mount Job, a subsidiary peak of Meager. The rock unit was formed during a period of rhyodacite volcanism during the Pleistocene epoch.Around Mount...
  
  
• The Devastator Assemblage
  The Devastator Assemblage
  The Devastator Assemblage is a geological formation comprising a portion of the Mount Meager massif in southwestern British Columbia, Canada. It is named after Devastator Peak , the lowest and southernmost subsidiary peak of Meager...
  
  
• Pylon Assemblage
  Pylon Assemblage
  The Pylon Assemblage is an accreted terrane of igneous rocks in southwestern British Columbia, Canada, located about north of Vancouver. It is named after Pylon Peak, a subsidiary summit of the Mount Meager massif...
  
  
• Volcanism of Western Canada
  Volcanism of Western Canada
  Volcanism of Western Canada produces lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds.-Volcanic belts:*Anahim...
  
  
• List of Cascade volcanoes
• List of volcanoes in Canada