The Bolivian tin belt ( es, Cinturón estanifero boliviano, provincia estannifera boliviana
) is a mineral-rich region in the
Cordillera Oriental of
Bolivia. Being a
metallogenetic province the Bolivian tin belt is rich in
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 ...
,
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 ...
,
silver
Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
and
base metal
A base metal is a common and inexpensive metal, as opposed to a precious metal such as gold or silver. In numismatics, coins often derived their value from the precious metal content; however, base metals have also been used in coins in the past ...
s. The Bolivian tin belt follows the same bend as the
Bolivian orocline.
[ The mineralizations of the belt were formed episodically beginning in the ]Triassic
The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...
and with the youngest known mineralizations dating to the Miocene
The Miocene ( ) is the first epoch (geology), 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 mea ...
.[
The mineral enrichment is a result of ]fluids
In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any she ...
expelled from 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. ...
magmas. Peraluminous magmas in turn results from the partial melting
Partial melting occurs when only a portion of a solid is melted. For mixed substances, such as a rock containing several different minerals or a mineral that displays solid solution, this melt can be different from the bulk composition of the soli ...
(anatexis
Anatexis (via Latin from Greek roots meaning "to melt down") is the partial melting of rocks. Traditionally, anatexis is used specifically to discuss the partial melting of crustal rocks, while the generic term "partial melting" refers to the par ...
) of metasedimentary rock
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 ...
and gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures a ...
in the continental crust
Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called '' sial'' be ...
.[ Analysis of ]trace element
__NOTOC__
A trace element, also called minor element, is a chemical element whose concentration (or other measure of amount) is very low (a "trace amount"). They are classified into two groups: essential and non-essential. Essential trace elements ...
s in the igneous rocks formed by this magma suggests that some of its material derives from melting of a pelitic rock of Lower Paleozoic age. Besides crustal components magmas did also involve sources in the mantle. The formation of these magmas is thus a form of crustal recycling.[
Peraluminous magmas are rare in 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 ...
but more common in collisional orogens such the Himalaya
The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 100 ...
s. From this it is inferred that the Andean orogeny
The Andean orogeny ( es, Orogenia andina) is an ongoing process of orogeny that began in the Early Jurassic and is responsible for the rise of the Andes mountains. The orogeny is driven by a reactivation of a long-lived subduction system alon ...
in Bolivia should have features in common with collisional orogens. This in turn might be related to particularities in the interaction of the South American Plate and the Nazca Plate during the Andean orogeny which led to collision-like events in the Cenozoic at the latitudes of Bolivia. The tectonic mechanism makes the invocation of a long-lived "tin anomaly" beneath the Cordillera Oriental unnecessary.
See also
*Cerro Rico
Cerro Rico (Spanish for "Rich Mountain"), Cerro Potosí ("Potosí Mountain") or Sumaq Urqu (Quechua ''sumaq'' "beautiful, good, pleasant", ''urqu'' "mountain", "beautiful (good or pleasant) mountain"), is a mountain in the Andes near the Bolivi ...
of Potosí
* El Indio Gold Belt
* Siglo XX mine
* Tin mining in Bolivia
References
{{Major South American geological formations
Belt regions
Geology of La Paz Department (Bolivia)
Geology of Oruro Department
Geology of Potosí Department
Metallogenetic provinces
Mining in Bolivia
Tin mining