The Napier Mountains are a group of close set peaks, the highest being Mount Elkins, at about 2,300 meters above sea level. This

mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have aris ...

is located in

Enderby Land Enderby Land is a projecting landmass of Antarctica. Its shore extends from Shinnan Glacier at about to William Scoresby Bay at , approximately of the earth's longitude (planets), longitude. It was first documented in western and eastern liter ...

, in the claimed

Australian Antarctic Territory The Australian Antarctic Territory (AAT) is a part of East Antarctica claimed by Australia as an external territory. It is administered by the Australian Antarctic Division, an agency of the federal Department of Climate Change, Energy, the E ...

East Antarctica East Antarctica, also called Greater Antarctica, constitutes the majority (two-thirds) of the Antarctic continent, lying primarily in the Eastern Hemisphere south of the Indian Ocean, and separated from West Antarctica by the Transantarctic ...

Location

The Napier Mountains are roughly four degrees west of Cape Boothby, Edward VIII Bay and Edward VIII Ice Shelf, and 3.5 degrees east of

Amundsen Bay Amundsen Bay, also known as Ice Bay, is a long embayment wide, close west of the Tula Mountains in Enderby Land, Antarctica. The bay was seen as a large pack-filled recession in the coastline by Sir Douglas Mawson on 14 January 1930. Seen by Ca ...

. The Napier Mountains are centered about 64 km south of Cape Batterbee in Enderby Land, East Antarctica. It extends about 64 km in a northwest–southeast direction from

Mount Codrington Mount Codrington () is a prominent mountain, high, standing south-southeast of Cape Close, east of Johnston Peak, and south of Simmers Peaks. Mount Codrington forms the northeastern end of the Napier Mountains. It was charted in 1930 by th ...

and includes Mount Kjerringa and the Young Nunataks.

Discovery

The Napier Mountains were discovered in January 1930 by the

British Australian New Zealand Antarctic Research Expedition The British Australian (and) New Zealand Antarctic Research Expedition (BANZARE) was a research expedition into Antarctica between 1929 and 1931, involving two voyages over consecutive Austral summers. It was a British Commonwealth initiative, d ...

under explorer

Douglas Mawson Sir Douglas Mawson (5 May 1882 – 14 October 1958) was a British-born Australian geologist, Antarctic explorer, and academic. Along with Roald Amundsen, Robert Falcon Scott, and Sir Ernest Shackleton, he was a key expedition leader during ...

. They were named by Mawson after John Mellis Napier, a judge of the

Supreme Court of South Australia The Supreme Court of South Australia is the superior court of the Australian state of South Australia. The Supreme Court is the highest South Australian court in the Australian court hierarchy. It has unlimited jurisdiction within the state in ...

. The mountain range was first visited by an

Australian National Antarctic Research Expeditions The Australian National Antarctic Research Expeditions (ANARE ) is the historical name for the Australia: Antarctic Program#Australian Antarctic program, Australian Antarctic Program (AAP) administered for Australia by the Australian Antarctic D ...

party in 1960. Members of this party included Syd Kirkby and Terence James Elkins.

Features

Geographic features of the Napier Mountains include: * Fitzgerald Nunataks * Grimsley Peaks * Mount Breckinridge *

* Mount Elkins * Mount Griffiths * Mount Maines * Mount Rabben * Skorefjell * Stor Hånakken Mountain * Wilkinson Peaks * Young Nunataks

Geology and orogeny

The Napier complex is among the most ancient terrestrial

terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its d ...

s on Earth. Its evolution is characterized by high-grade

metamorphism Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated ...

and several strong deformations. At least four distinct tectonothermal events occurred in the Archaean eon: # 3.8 billion years ago (Ga): occurrence of initial

felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...

igneous activity Volcanism, vulcanism, volcanicity, or volcanic activity is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. It is caused by the presence of a he ...

over a long period of time # 3.0 Ga: emplacement of

charnockite Charnockite () is any orthopyroxene-bearing quartz-feldspar rock formed at high temperature and pressure, commonly found in granulite facies’ metamorphic regions, ''sensu stricto'' as an endmember of the charnockite series. Charnockite seri ...

at Proclamation Island # 2.8 Ga: occurrence of a very-high grade discrete tectonothermal event (an ultra-high temperature metamorphic event) # 2.5 Ga: occurrence of a subsequent, protracted high-grade tectonothermal event Much of the East Antarctic craton was formed in the

Precambrian The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...

by a series of tectonothermal orogenic events. Napier orogeny formed the cratonic nucleus approximately 4 Ga. Mount Elkins is a classic example of Napier orogeny. Napier orogeny is characterized by high-grade metamorphism and

plate tectonics Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

. The orogenic events which resulted in the formation of the Napier complex (including Mount Elkins) have been dated to the Archean. Radiometrically dated to as old as 3.8 billion years, some of the

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...

s collected from the orthogneisses of Mount Sones are among the oldest rock specimens found on Earth. Billions of years of

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

and tectonic deformation have exposed the

metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...

core of these ancient mountains. The oldest crustal components found to date in the Napier complex appear to be of

igneous Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

derivation. This rock appears to have been overprinted by an ultra-high temperature metamorphic event (UHT) that occurred near the Archean-Proterozoic boundary. Using a lutetium-hafnium (Lu-Hf) method to examine

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. Garnet minerals, while sharing similar physical and crystallographic properties, exhibit a wide range of chemical compositions, de ...

orthopyroxene The pyroxenes (commonly abbreviated 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 ions of calcium (Ca), sodium (Na), iron (Fe( ...

, sapphirine, osumilite and

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at vis ...

from this UHT

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 ...

belt, Choi ''et al'' determined an

isochron In the mathematical theory of dynamical systems, an isochron is a set of initial conditions for the system that all lead to the same long-term behaviour. Mathematical isochron An introductory example Consider the ordinary differential equation ...

age of 2.4 billion years for this metamorphic event. Using SHRIMPU–Pb zircon dating methodology, Belyatsky ''et al'' determined the oldest tectonothermal event in the formation of the Napier Complex to have occurred approximately 2.8 Ga. Preservation of the UHT mineral assemblage in the analyzed rock suggests rapid cooling, with closure likely to have occurred for the Lu-Hf system at post-peak UHT conditions near a

closure temperature In radiometric dating, closure temperature or blocking temperature refers to the temperature of a system, such as a mineral, at the time given by its radiometric date. In physical terms, the closure temperature is the temperature at which a syste ...

of 800 °C. UHT granulites appear to have evolved in a low Lu-Hf environment, probably formed when the rocks were first extracted from a mantle profoundly depleted in lithophile elements. The source materials for the

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

s that formed the Napier Complex were extremely depleted relative to the chondritic uniform reservoir. These results also suggest significant depletion of the early Archean mantle, in agreement with the early

igneous differentiation In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement, or eruption. The sequence of ...

of the Earth that the latest core formation models require.

References

External links

Australian Antarctic Names and Medals Committee (AANMC)

Australian Antarctic Gazetteer

United States Geological Survey, Geographic Names Information System (GNIS)

Scientific Committee on Antarctic Research (SCAR)

PDF Map of the Australian Antarctic Territory

Mawson Station
{{usgs-gazetteer Mountain ranges of Enderby Land