The Birch Mountains kimberlite field is a cluster of kimberlitic volcanic pipes or diatremes in north-central Alberta, Canada that were emplaced during a period of kimberlitic volcanism in the Late Cretaceous epoch. [1] As of 2011, 8 diatremes had been discovered in the field, and diamonds and microdiamononds had been recovered during sampling programs. [2]
The Birch Mountain (BM) kimberlite field was discovered in 1998 and lies about 430 km (270 mi) north of Edmonton and 135 km (84 mi) northwest of Fort McMurray. It is part of the Northern Alberta kimberlite province, along with the Buffalo Head Hills kimberlite field and the Mountain Lake cluster. [2]
The BM diatremes are hosted in the marine shales and silty shales of the Late Cretaceous Smoky or La Biche Group, and they are thought to have been erupted in an open marine to near shore marine setting in the Western Interior Seaway. Unconsolidated Quaternary sediments that reach thicknesses of more than 150 m (490 ft) now cover the bedrock in the area, so the diatremes were located primarily by aeromagnetic surveys followed by drilling. [2]
According to radiometric dating the BM diatremes were emplaced about 70 to 78 million years ago during the Campanian to Maastrichtian stages of the Late Cretaceous epoch. Microfossils from shales interbedded with kimberlite at some of the diatremes are consistent with a Late Cretaceous age (Late Albian to Maastrichtian). [2]
The volcanic rocks of the BM field consist primarily of crater-facies pyroclastic kimberlite and resedimented kimberlite. They include massive layers, as well as bedded and graded layers of coarse lapilli alternating with layers of finer tuff. Lapilli and olivine phenocrysts are set in a grey-green matrix of serpentine, carbonate minerals (calcite, dolomite, and magnesite) and clay minerals. Phlogopite, oxide minerals (ilmenite, perovskite and spinel), apatite and pyrite are also present. Diamonds and microdiamonds have been recovered from samples taken from the Phoenix and Legend pipes. [2]
The diatremes within the field include:
Kimberlite is an igneous rock, which sometimes contains diamonds. It is named after the town of Kimberley in South Africa, where the discovery of an 83.5-carat (16.70 g) diamond called the Star of South Africa in 1869 spawned a diamond rush and the digging of the open-pit mine called the Big Hole. Previously, the term kimberlite has been applied to olivine lamproites as Kimberlite II, however this has been in error.
The Maastrichtian is, in the ICS geologic timescale, the latest age of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned the interval from 72.1 to 66 million years ago. The Maastrichtian was preceded by the Campanian and succeeded by the Danian.
Northern Alberta is a region located in the Canadian province of Alberta.
The volcanism of Canada is represented by many types of landform including lava flows, volcanic 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. It has a very complex volcanic history spanning from the Precambrian eon at least 3.11 billion years ago when this part of the North American continent began to form.
The Geology of Kansas encompasses the geologic history of the US state of Kansas and the present-day rock and soil that is exposed there. Rock that crops out in Kansas was formed during the Phanerozoic eon, which consists of three geologic eras: the Paleozoic, Mesozoic and Cenozoic. Paleozoic rocks at the surface in Kansas are primarily from the Mississippian, Pennsylvanian and Permian periods.
The Phoenix pipe is a diatreme associated with the Birch Mountains kimberlite field in northern Alberta, Canada. It is thought to have formed about 75 million years ago when this part of Alberta was volcanically active during the Late Cretaceous period.
The Valkyrie pipe is a diatreme in northern Alberta, Canada. It is associated with a group of diatremes called the Birch Mountains kimberlite field which is thought to have formed about 75 million years ago when this part of Alberta was volcanically active during the Late Cretaceous period.
The Legend pipe is a diatreme associated with the Birch Mountains kimberlite field in northern Alberta, Canada. It is thought to have formed about 75 million years ago during the Late Cretaceous period.
The Xena pipe is a diatreme associated with the Birch Mountains kimberlite field in northern Alberta, Canada. It is thought to have formed about 75 million years ago when this part of Alberta was volcanically active during the Late Cretaceous period.
The Dragon pipe is a diatreme associated with the Birch Mountains kimberlite field in northern Alberta, Canada. It is thought to have formed about 75 million years ago when this part of Alberta was volcanically active during the Late Cretaceous period.
The Buffalo Head Hills kimberlite field is a group of kimberlitic volcanic pipes or diatremes in north-central Alberta, Canada. As of 2011, 41 kimberlite pipes, of which 28 are diamondiferous, had been identified in the field. They were emplaced during Late Cretaceous to early Paleocene time.
The Kendu pipe is a diatreme associated with the Birch Mountains kimberlite field in northern Alberta, Canada. It is thought to have formed about 75 million years ago when this part of Alberta was volcanically active during the Late Cretaceous period.
K6 pipe is a diamondiferous diatreme in the Buffalo Head Hills kimberlite field of Northern Alberta, Canada. It is thought to have formed about 85 million years ago when is part of Alberta was volcanically active during the Late Cretaceous period. It is typical of melts that originated from the low mantle.
The Northern Alberta Kimberlite Province (NAKP) consists of three groups of diatremes or volcanic pipes in north-central Alberta, Canada, most of which are kimberlites and some of which are diamondiferous. They are called the Birch Mountains (BM), Buffalo Head Hills (BHH), and the Mountain Lake cluster (ML), and they were discovered between about 1990 and 1997. Most of the diatremes were emplaced during the Late Cretaceous Epoch although a few are as young as early Paleocene.
K252 pipe is a diamondiferous diatreme in the Buffalo Head Hills kimberlite field of Northern Alberta, Canada. It is thought to have formed about 85 million years ago when this part of Alberta was volcanically active during the Late Cretaceous period. It contains pyroclastic textures and is intruded into Cenomanian and Albian aged strata.
K19 pipe is a diatreme in the southwestern part of the Buffalo Head Hills kimberlite field in Northern Alberta, Canada. It is thought to have formed about 60 million years ago, making it one of the youngest volcanic formations in the Buffalo Head Hills kimberlite field and in Alberta. Unlike many other diatremes in the Buffalo Head Hills kimberlite field, it contains low diamond content.
The Lac de Gras kimberlite field is a group of Late Cretaceous to Eocene age diatremes in the Northwest Territories, Canada.
The Mountain Lake cluster consists of two diatremes or volcanic pipes in Northern Alberta, Canada. It was emplaced during a period of kimberlite volcanism in the Late Cretaceous epoch.
Volcanism of Western Canada has produced lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, greenstone belts, submarine volcanoes, calderas, diatremes and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds.
The Igwisi Hills are a volcanic field in Tanzania. Three tuff cones are found there, one of which is associated with a lava flow. They are one of the few locations of possibly kimberlitic lava flows on Earth.