The Jack Hills are a range of hills in Mid West Western Australia

Western Australia

Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...

. They are best known as the source of the oldest material of terrestrial origin found to date: zircon

Zircon

Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y...

s that formed around 4.4 billion years ago. These zircons have enabled ground-breaking research into the conditions on earth in the Hadean

Hadean

The Hadean is the geologic eon before the Archean. It started with the formation of the Earth about 4.7 Ga and ended roughly 3.8 Ga, though the latter date varies according to different sources. The name "Hadean" derives from Hades, Greek for "Underworld", referring to the "hellish"...

 eon.

Geography

They are located on the border of the Shire of Murchison

Shire of Murchison

The Shire of Murchison is a large agricultural region in the central part of Western Australia, and is the only shire in Australia without a town. At the 2006 Census, it was also the least populous Local Government Area in Western Australia.-Description:...

 and the Shire of Meekatharra

Shire of Meekatharra

The Shire of Meekatharra is a Local Government Area in the Mid West region of Western Australia, about halfway between the town of Port Hedland and the state capital, Perth, Western Australia. The Shire covers an area of , and its seat of government is the town of Meekatharra.-History:The...

, south of the Murchison River

Murchison River (Western Australia)

The Murchison River is the second longest river in Western Australia. It flows for about from the southern edge of the Robinson Ranges to the Indian Ocean at Kalbarri. It has a mean annual flow of about 200 million cubic metres.-Course:...

, about 800 kilometres north of Perth

Perth, Western Australia

Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....

.

Geology

The Jack Hills are located in the Narryer Gneiss Terrane

Narryer Gneiss Terrane

The Narryer Gneiss Terrane is a geological complex in Western Australia that is composed of a tectonically interleaved and polydeformed mixture of granite, mafic intrusions and metasedimentary rocks in excess of 3.3 billion years old, with the majority of the Narryer Gneiss Terrane in excess of 3.6...

 of the Yilgarn Craton

Yilgarn craton

The Yilgarn Craton is a large craton which constitutes the bulk of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts...

, Western Australia

Western Australia

Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...

, and comprise an 80 km long northeast-trending belt of folded

Fold (geology)

The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in...

 and metamorphosed

Metamorphism

Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...

 supracrustal rock

Supracrustal rock

Supracrustal rocks are rocks that were deposited on the existing basement rocks of the crust, hence the name. They may be further metamorphosed from both sedimentary and volcanic rocks....

s.

Sedimentary siliciclastic rocks, interpreted as alluvial fan-delta

River delta

A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...

 deposits, are the major lithology. Minor mafic

Mafic

Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...

/ultramafic rocks and banded iron formation

Banded iron formation

Banded iron formations are distinctive units of sedimentary rock that are almost always of Precambrian age. A typical BIF consists of repeated, thin layers of iron oxides, either magnetite or hematite , alternating with bands of iron-poor shale and chert...

 (BIF) are also found in the sequence. The overall sequence is generally considered to be a granulite

Granulite

Granulites are medium to coarse–grained metamorphic rocks that have experienced high temperature metamorphism, composed mainly of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure...

 gneiss, which has undergone multiple deformations and multiple metamorphic episodes. The protolith age of the Narryer Gneiss Terrane is variable, but generally considered to be in excess of 3.6 Ga (billion years).

Oldest zircons on earth

Detrital zircon

Zircon

Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y...

s with ages greater than 4 billion years old have been found in these rocks, and a 4,404 (+/-8) billion year old zircon was found at Eranondoo Hill; this is the oldest dated material

Oldest rock

The oldest dated rocks on Earth, as an aggregate of minerals that have not been subsequently melted or disaggregated by erosion, are from the Archean Eon. Such rocks are exposed on the surface in very few places....

 originating on Earth; the date is in the Cryptic era

Cryptic era

The Cryptic era is an informal term that refers to the earliest geologic evolution of the Earth and Moon. It is the oldest era of the Hadean eon, and it is commonly accepted to have begun close to 4567.17 million years ago when the Earth and Moon formed...

 of the Hadean

Hadean

The Hadean is the geologic eon before the Archean. It started with the formation of the Earth about 4.7 Ga and ended roughly 3.8 Ga, though the latter date varies according to different sources. The name "Hadean" derives from Hades, Greek for "Underworld", referring to the "hellish"...

 eon. They were found within a unit of the supracrustal sequence, a metamorphosed conglomerate considered to have an age ~3.0 Ga. Given the detrital nature of the rock unit, the zircons are sourced from pre-existing rocks which were then weathered and the resultant sediment deposited as sedimentary rock.

The zircons and various aspects of their geochemistry provide evidence for the existence of continental-type crust on the surface of the earth during the Hadean eon, contrasting with earlier ideas on the earliest phase of Earth's history

History of Earth

The history of the Earth describes the most important events and fundamental stages in the development of the planet Earth from its formation 4.578 billion years ago to the present day. Nearly all branches of natural science have contributed to the understanding of the main events of the Earth's...

. Additionally, oxygen isotopic ratios in the zircons provide evidence for the presence of liquid water on the surface, if not a water ocean; also contrasting with earlier ideas on Earth's history

History of Earth

The history of the Earth describes the most important events and fundamental stages in the development of the planet Earth from its formation 4.578 billion years ago to the present day. Nearly all branches of natural science have contributed to the understanding of the main events of the Earth's...

. The theory of humid and cool conditions before the Late Heavy Bombardment

Late Heavy Bombardment

The Late Heavy Bombardment is a period of time approximately 4.1 to 3.8 billion years ago during which a large number of impact craters are believed to have formed on the Moon, and by inference on Earth, Mercury, Venus, and Mars as well...

 has been promoted as Cool Early Earth

Cool Early Earth

The Cool Early Earth theory posits that the early planet Earth had a calm influx of bolides and a cool climate allowing fluid water, after the planetary accretion but before the occurrence of the Late Heavy Bombardment in the Hadean geological eon. The Cool Early Earth is believed to have been the...

.

Economic geology

The Jack Hills banded iron formation is the site of a minor iron ore mine operated by Crosslands Resources (a 50:50 venture between Murchison Mines and Mitsubushi Development) which is exporting 3 million tonnes per annum of high grade detrital hematite

Hematite

Hematite, also spelled as haematite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...

 iron ore via the port of Geraldton. The company plans to expand the operation to include extraction of the magnetite

Magnetite

Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...

 bearing BIF.

Other companies operating in the area are also planning major magnetite BIF based iron ore mines

Conservation

Because of their importance as a geology research site, the Jack Hills were nominated to the Register of the National Estate

Register of the National Estate

The Register of the National Estate is a listing of natural and cultural heritage places in Australia. The listing was initially compiled between 1976 and 2003 by the Australian Heritage Commission. The register is now maintained by the Australian Heritage Council...

in 2003. At present they have an Interim Listing, which means they have been formally proposed for inclusion in the Register.