Cerro Aspero Batholith ( es, batolito de Cerro Aspero) is a group of
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 ...
s in southern
Sierras Pampeanas
The Sierras Pampeanas (also called Central Sierras or Pampas Sierras) (English: Pampas Mountains) is a geographical region of Argentina.
The Sierras Pampeanas are a chain of mountains that rise sharply from the surrounding pampa region of ...
in central Argentina. The
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 ...
covers an approximate area of 440 km2 and lies about 50 km south of the larger Achala Batholith. The batholith contains various circular plutons emplaced by stoping at pressures of 2
kbar
The bar is a metric unit of pressure, but not part of the International System of Units (SI). It is defined as exactly equal to 100,000 Pa (100 kPa), or slightly less than the current average atmospheric pressure on Earth at sea lev ...
or less. Alpa Corral, El Talita and Los Cerros are the three largest individual plutons and together they make up the bulk of the batholith. The most common rock type is
monzogranite
Monzogranites are biotite granite rocks that are considered to be the final fractionation product of magma. Monzogranites are characteristically felsic (SiO2 > 73%, and FeO + MgO + TiO2 < 2.4), weakly
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 an igneous
texture
Texture may refer to:
Science and technology
* Surface texture, the texture means smoothness, roughness, or bumpiness of the surface of an object
* Texture (roads), road surface characteristics with waves shorter than road roughness
* Texture (c ...
that is
equigranular
An equigranular material is composed chiefly of crystals of similar orders of magnitude to one another. Basalt and gabbro
Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-ric ...
but varies from coarse grained to
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 all ...
.
The emplacement of plutons occurred in the Middle to Late
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
period.
Contact aureole
Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of chem ...
s for the batholith are, contrary to other batholiths, largely undeformed. The relation of the magmatic episode represented by the Cerro Aspero Batholith to the
Famatinian orogeny
The Famatinian orogeny ( es, Orogenia de Famatina) is an orogeny that predates the rise of the Andes and that took place in what is now western South America during the Paleozoic, leading to the formation of the Famatinian orogen also known as ...
is not fully understood. Alternatively it is grouped as a "Achaliano" igneous cycle.
Vertical to near-vertical veins of
fluorite
Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon.
The Mohs sca ...
formed in the
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 ...
occur in the batholith. At most veins reach 3 meters in thickness. Collectively these veins constitute the largest reserves of fluorite in the whole
Sierras Pampeanas
The Sierras Pampeanas (also called Central Sierras or Pampas Sierras) (English: Pampas Mountains) is a geographical region of Argentina.
The Sierras Pampeanas are a chain of mountains that rise sharply from the surrounding pampa region of ...