Kari-Kari is a

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

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 ...

in the

Potosi department Potosí or Potosi may refer to: Places United States * Potosi, Missouri, in Washington County * Potosi, Nevada, a ghost town in Clark County, Nevada * Potosi, Texas, in Taylor County * Potosi (town), Wisconsin, in Grant County ** Potosi, ...

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

. It is part of the El Fraile ignimbrite field of the

Central Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South Americ ...

of the

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

. Volcanic activity in the Central Volcanic Zone has generated 44 volcanic centres with postglacial activity and a number of calderas, including the Altiplano-Puna volcanic complex. Kari-Kari is a caldera whose dimensions are variously considered to be or . After emplacement of the caldera, intrusive activity generated the Kari-Kari dome which was originally considered to be a

batholith A batholith () is a large mass of intrusive igneous rock (also called plutonic rock), larger than in area, that forms from cooled magma deep in Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock types, such ...

. Mineralization reactions have formed a number of mineral deposits at

Cerro Rico Cerro Rico (Spanish for "Rich Mountain"), Cerro Potosí ("Potosí Mountain") or Sumaq Urqu (Quechuan languages, Quechua ''sumaq'' "beautiful, good, pleasant", ''urqu'' "mountain", "beautiful (good or pleasant) mountain"), is a mountain in the A ...

and inside the caldera.

Geography and structure

Kari-Kari is located close to Potosi, according to one reconstruction the city lies within the caldera. With an age of 21,000,000 years it is the oldest caldera structure that has been identified with unaided

satellite imagery Satellite images (also Earth observation imagery, spaceborne photography, or simply satellite photo) are images of Earth collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell ima ...

. It is part of the

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 ...

province of the Miocene Central Andes, which includes also the Altiplano-Puna volcanic complex with an estimated volume of . Kari-Kari belongs to a more peraluminous domain of the ignimbrite provinces of the Central Andes, which also includes the Los Frailes ignimbrite field. Specifically, Kari-Kari is located in the Eastern Cordillera. Other ignimbrite fields north of 21° southern latitude are the

Macusani Macusani is a town in Southern Peru, capital of the province Carabaya in the region Puno Puno (Aymara and qu, Punu) is a city in southeastern Peru, located on the shore of Lake Titicaca. It is the capital city of the Puno Region and the Puno ...

(10,000,000–6,700,000 years ago in Peru) and

Morococala Morococala is a volcanic field in Bolivia, in the Department Oruro. It is formed by ignimbrites and associated volcanic features. It is part of the chain of plutons that extends over the Cordillera Real and the Cordillera Occidental and are the ...

(~8,000,000–6,000,000 years ago in Bolivia) fields. These ignimbrites are part of one domain of the Central Volcanic Zone, the other two domains are the principal

andesitic 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 ...

volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...

and a scattered

back-arc A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most of ...

volcanic region. Volcanic activity within the Kari-Kari-Fraile region may be influenced by extensional tectonics. The Kari-Kari caldera is ellipse-shaped and has a

granitoid 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 ...

complex also named Kari-Kari at its centre. The caldera itself has dimensions of . Other dimensions given are . The caldera has a so-called

trapdoor A trapdoor is a sliding or hinged door in a floor or ceiling. It is traditionally small in size. It was invented to facilitate the hoisting of grain up through mills, however, its list of uses has grown over time. The trapdoor has played a pivot ...

morphology. Outflow sheets surround the caldera on its northern and northwestern side. The Kari-Kari dome was originally assumed to be a batholith; later it is being interpreted as a resurgent ignimbrite structure. It has dimensions of and is formed by a

pluton 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 ...

inside the welded ignimbrite, reaching thicknesses of over , with a total uplift of about . The dome reaches altitudes of over , and effects of

glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...

and

moraine A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice shee ...

cover are noticeable and did conceal the true nature of the dome for a while. Farther south a true intrusion called the Kumurana is also located. The Cerro Rico intrusion is found west of Kari-Kari and was previously linked to the Kari-Kari

ring fault Ring may refer to: * Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry * To make a sound with a bell, and the sound made by a bell :(hence) to initiate a telephone connection Arts, entertainment and media Film and ...

, but mapping published in 2000 suggests that it formed away from the Kari-Kari ring fault and may be an independent centre. The Kari-Kari and Canteria tuffs and tuff-

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 di ...

s are associated with the caldera. The formation of Kari-Kari may have been influenced by deep seated faults which form lineaments visible at the surface. The composition of the so-called Caracoles formation at Kari-Kari indicates the caldera may have been filled by a

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...

for a while. The Lago Chalviri is located within the caldera, at the foot of the dome. Laguna Ulistia is another lake in the caldera. The Cordillera Andacaba area in the southern caldera is the site of several mining districts, which include

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

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 ...

rich areals. The Kumurana mine is located in the southern part of the caldera, its mineralization occurred at temperatures of . The Cerro Rico stock has been extensively hydrothermally modified and a number of

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...

s are found there. It was a major source of

silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...

for

Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...

in the 16th and 17th century. Mining has been ongoing for over 450 years. Starting from 1912

has been mined as well. Other mines in the dome are Lord Byron, Carandaiti, Mazuni, Illimani and Chaquirana.

Geology

The

Andean Volcanic Belt The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South Americ ...

is typically subdivided into four sectors, the Northern Volcanic Zone, the Central Volcanic Zone and two southern Volcanic Zones. In Bolivia's

Altiplano The Altiplano (Spanish for "high plain"), Collao (Quechua and Aymara: Qullaw, meaning "place of the Qulla") or Andean Plateau, in west-central South America, is the most extensive high plateau on Earth outside Tibet. The plateau is located at the ...

, volcanic activity commenced 26,000,000 years ago as part of the Central Volcanic Zone. Approximately 44 volcanic centres in the Central Volcanic Zone show evidence of post-glacial activity. The main ignimbrite volcanic structure of the Central Volcanic Zone is the Altiplano-Puna volcanic complex. Other ignimbritic volcanic systems are the Galan and Panizos calderas, as well as older

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

ignimbrites in Sur Lipez. Kari-Kari is part of a volcanic system with neighbouring Los Frailes volcanic system, which has been active starting from 25,000,000 to recent times over six phases, covering a surface area of . Kari-Kari is the earliest known caldera in the Eastern Cordillera. No volcanic ignimbrites younger than 3,800,000 million years are found in the Eastern Cordillera, although in the Frailes region volcanic activity has continued into the

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

with the

Nuevo Mundo volcano Nuevo Mundo also known as Jatun Mundo Quri Warani (Hispanicized spellings ''Jatun Mundo Khori Huarani, Jatun Mundo Khorihuarani''), is a stratovolcano, lava dome and a lava flow complex between Potosí and Uyuni, Bolivia, in the Andes rising to a ...

. Alternatively, Kari-Kari has been classified as a lower Miocene volcanic province that also includes

Illimani Illimani (Aymara) is the highest mountain in the Cordillera Real (part of the Cordillera Oriental, a subrange of the Andes) of western Bolivia. It lies near the cities of El Alto and La Paz at the eastern edge of the Altiplano. It is the secon ...

and several other volcanic centres. The basement has been analyzed at the neighbouring centre of Cerro Rico, where

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

s and other

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

and

Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

formations form much of the basement. Three different

craton A craton (, , or ; from grc-gre, κράτος "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and ...

s named

Arequipa-Antofalla Arequipa-Antofalla is a basement unit underlying the central Andes in northwestern Argentina, western Bolivia, northern Chile and southern Peru. Geologically, it corresponds to a craton, terrane or block of continental crust. Arequipa-Antofalla ...

, Brazilian and Pampean underpin Bolivia and the Huarina belt, which is the zone that separates these cratons. Rocks from the cratons have influenced the composition of Cerro Rico stocks.

Composition

Kari-Kari has erupted welded tuffs that contain

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...

. The so-called "moat deposit" also contains large

clast Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks ...

s and an ash-fall deposit resulting from an

eruption column An eruption column or eruption plume is a cloud of super-heated ash and tephra suspended in gases emitted during an explosive volcanic eruption. The volcanic materials form a vertical column or plume that may rise many kilometers into the air a ...

collapse. The red-purple Canteria ignimbrite has similar composition but contains much less clastic components. The Kari-Kari tuffs fit the general pattern of El Fraile associated tuffs being

Europium Europium is a chemical element with the symbol Eu and atomic number 63. Europium is the most reactive lanthanide by far, having to be stored under an inert fluid to protect it from atmospheric oxygen or moisture. Europium is also the softest lanth ...

in Cerro Rico may have been contributed to by the Kari-Kari pluton.

Potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

content in the rocks reaches 11%. The Kari-Kari dome is formed by

dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...

rhyodacite Rhyodacite is a volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of those plutonic rocks that are intermediate in composition between monzogranite and granodiorite. Rhyodacites form from rapid ...

as well as

granodiorite Granodiorite () is a coarse-grained (phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. The term banatite is sometimes used informally for various rocks ranging from gra ...

. Lead, tin and zinc form small veins in the dome.

Fiamme Fiamme are lens-shapes, usually millimetres to centimetres in size, seen on surfaces of some volcaniclastic rocks. They can occur in welded pyroclastic fall deposits and in ignimbrites, which are the deposits of pumiceous pyroclastic density cu ...

s of

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 alumino ...

and

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more prope ...

stand out above the matrix that contains garnet and plagioclase. It also contains

xenolith A xenolith ("foreign rock") is a rock fragment (country rock) that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term ''xenolith'' is almost exclusively used to describe inclusions in igne ...

s both from Agua Dulce lavas and

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

sediments. The Kumurana intrusion has a composition between granodiorite and

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 form ...

monzonite Monzonite is an igneous intrusive rock, formed by slow cooling of underground magma that has a moderate silica content and is enriched in alkali metal oxides. Monzonite is composed mostly of plagioclase and alkali feldspar. Syenodiorite is an o ...

. Overall, the Kari-Kari rocks are

peraluminous Peraluminous rocks are igneous rocks that have a molecular proportion of aluminium oxide higher than the combination of sodium oxide, potassium oxide and calcium oxide.Blatt, Harvey and Robert J. Tracy, ''Petrology,'' Freeman, 2nd ed., 1995, p. ...

and originated from the

amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose (flaky ...

granulite Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are medium to coarse–grained and mainly composed of feldspars sometimes associated w ...

segment of the crust under the influence of magmatic underplating. Differentiation along

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 ...

and peraluminous phases formed the eventual magma. The magma was predominantly formed from crustal phases. content per weight is between 58–65%. These rocks were subsequently subject to hydrothermal alteration by

boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...

- and

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

-rich fluids which in multiple stages formed the mineral veins.

Eruptive history

Activity in the Kari-Kari and neighbouring Los Frailes ignimbrite plateau spans 17,000,000 – 2,000,000 years ago. The Kari-Kari

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 cont ...

s themselves were dated 20,100,000 – 21,950,000 years ago. These crystal rich welded tuffs accumulated within the caldera and have a volume of about . The Kari-Kari dome and Kumurana plutons were formed between 23,000,000 and 21,000,000 years ago. The Agua Dulce volcanics are of similar ages as the Kari-Kari dome, as is the Canteria ignimbrite. A weighed age estimate for the Agua Dulce, Kari-Kari, Kumurana and Canteria formations is 21,400,000 ± 400,000 years ago. Older ages of 42,510,000 to 45,480,000 are found in dykes and may reflect the age at which the pluton was emplaced. The Cerro Rico intrusion is 7,000,000 years younger than the main Kari-Kari caldera.

References

External links

* {{cite web, title=Kari-Kari Caldera, url=http://volcano.oregonstate.edu/oldroot/CVZ/karikari/index.html, website=Volcano World, publisher=Oregon State University, accessdate=15 June 2016 Calderas of Bolivia Miocene calderas Potosí Department Volcanoes of Potosí Department