Lodranites are a small group of

primitive achondrite Primitive achondrites are a subdivision of meteorites. They are classified on the same rank (historically called "Class") and lying between chondrites and achondrites. They are called primitive because they are achondrites that have retained much o ...

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object en ...

s that consists of

meteoric iron Meteoric iron, sometimes meteoritic iron, is a native metal and early-universe protoplanetary-disk remnant found in meteorites and made from the elements iron and nickel, mainly in the form of the mineral phases kamacite and taenite. Meteoric i ...

and

silicate mineral Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consi ...

Olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...

and

pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...

make up most of the silicate minerals. Like all

s lodranites share similarities with

chondrites A chondrite is a stony (non-metallic) meteorite that has not been modified, by either melting or differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form primi ...

and achondrites.

Naming and history

The lodranite group is named after Lodhran,

Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...

, where the type specimen fell on 1 October 1868 at 14:00. Eyewitnesses of the fall reported a loud bang accompanied by a rising dust cloud to the east of the city, which led to the discovery and retrieval of the meteorite. The "meteorite from Lodran" was first described by

Gustav Tschermak Gustav Tschermak von Seysenegg (19 April 1836 – 24 May 1927) was an Austrian mineralogist. Biography He was born in Litovel, Moravia, and studied at the University of Vienna, where he obtained a teaching degree. He studied mineralogy at Heidel ...

in 1870. He described the meteorite being "''apart from the nickel-iron it is an

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...

bronzite Bronzite is a member of the pyroxene group of minerals, belonging with enstatite and hypersthene to the orthorhombic series of the group. Rather than a distinct species, it is really a ferriferous variety of enstatite, which owing to partial alte ...

aggregates of such outstanding sort, that has never been found in a meteorite before only similar to the terrestrial olivine rock''". George Thurland Prior was the first to classify the lodran meteorite as the only member of the lodranite group. He also saw close similarities to the ureilites.

Description

Lodranites are primitive achondrites. They are coarser grained than acapulcoites. The main mineral phases are low calcium pyroxene and olivine with minor amounts of

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 pro ...

and

troilite Troilite is a rare iron sulfide mineral with the simple formula of FeS. It is the iron-rich endmember of the pyrrhotite group. Pyrrhotite has the formula Fe(1-x)S (x = 0 to 0.2) which is iron deficient. As troilite lacks the iron deficiency whic ...

. Because of their composition they are related to the

and H class chondrites. Lodranites can be described as chondrites that were heated to the point where FeNi and FeS reach a eutectic point. At this point partial melting occurred and some of the metal- and silica melt was removed. The Lodran meteorite is described as having roughly equal amounts of metal,

and

which make up most of the volume. Other minerals include sulphide, chromite, phosphide and chrome-diopside.

Parent body

The lodranites and acapulcoites share the same parent body which was probably similar to an

S-type asteroid S-type asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the secon ...

. The lodranites are coarser grained and yield higher temperatures with isotopic methods and are therefore thought to be from greater depths within the parent body. The cooling path of the parent body can be reconstructed by using

radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares t ...

. The Hf-W system in high-Ca pyroxenes has a closing temperature in between 975 and 1025 °C. The parent body cooled under this temperature between 4563.1 and 4562.6 million years ago. This means that the parent body accreted about 1.5 to 2 million years after the CAI formation. Trace elements indicate that the parent body had a complex geologic history with partial melting, melt migration and

metasomatism Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is the replacement of one rock by another of different mineralogical and chemical c ...

References

{{Meteorites Achondrite meteorites

Naming and history

Description

Parent body

See also

References