Jack Hills, Nookawarra Station, Murchison Shire, Western Australia, Australiai

Regional Level Types
Jack Hills	Group of Hills
Nookawarra Station	- not defined -
Murchison Shire	Shire
Western Australia	State
Australia	Country

The Mindat co-ordinates mark Eranondoo Hill near where the zircons were found. The exact spot of the zircon discovery is very specific, and it is not possible with the level of accuracy needed to mark on Mindat. Google Maps spells the hill as Erawondoo.

Located approximately 200 kilometres west north-west of Meekatharra. Jack Hills is 80 kilometres long, north-east trending belt of folded and metamorphised supracrustal rock. The hills are composed of sedimentary siliciclastic rocks, with minor mafic/ultramafic rocks, and banded iron formations.

Some of the zircon crystals in these rocks (which are over 3 billion years old) are even older, ~4.4 billion years, and therefore stem from similarly old rocks. These zircons represent the oldest known mineral on Earth at only 150 million years after the formation of the planet. The presence of zircon crystals within these rocks appears to contradict the notion that the first 500 million years of Earth's history- the Hadean Eon - was a continuously violent and chaotic time, where volcanism and meteorite impact meant a global magma ocean on the planet surface. The chemical make-up of the Jack Hills crystals suggests they were formed in the presence of liquid water, and provide evidence the Earth was cooler and wetter than we used to think. This in turn could mean life evolved far earlier than we know at present.

The crystals were discovered in the early 1980s, but their significance was not immediately apparent. They had been weathered out of rocks, and found in river sediment. The rock host is over 3 billion years old. Later the zircons were dated at 4.1 billion years, which while old, compared to rocks found elsewhere of the same age. Eventually new techniques, proved some of the zircons from Eranondoo Hill to be 4.4 billion years old, the oldest material found on Earth (Wilde et al., 2001).

(Allegedly four billion year old micro diamond inclusions in the Jack Hill zircon rock have also been discovered through work by Perth's Curtin University geology department, and the University of Munster mineralogy department in Germany. They were thought to be the oldest known diamonds, but are actually remnants of polishing powder that infiltrated minute fissures in the zircon crystals.)

In 2001, analysis of the relative amounts of different isotopes of oxygen indicated the ratio was skewed heavily towards oxygen 18, as opposed to the more common light oxygen 16. This indicates the rocks formed in a cool, wet, sedimentary process on the Earth's surface. The magma which gave rise to the zircons may have formed on an ocean floor, and cooled quickly. It also highlights the magma was from recycled rock that had interacted with the surface water and not from a mantle source. The presence of quartz inclusions, as well as results from neodymium and hafnium isotopic studies support a felsic source suggesting continental crust may have been forming very early in Earth's history, along with tectonic processes like subduction.

Inclusions in these zircons are not magmatic, but formed during metamorphism at either 2.68 Ga or 0.8 Ga (Rasmussen et al. 2011).

The C isotopic composition of primary graphite inclusions in a >3.8-Ga zircon was inferred to be consistent with a biogenic origin and may be evidence that a terrestrial biosphere had emerged by 4.1 Ga, or ∼300 My earlier than has been previously proposed (Bell et al. 2015).

Zircons are extremely durable. They are single grained size and not visible to the naked eye in the rocks. Zircons from Jack Hills are on display at the Natural History Museum in Vienna, as part of a permanent exhibit "Evolution of Minerals."

Geochronology

Mineralization age: Basin Groups to Tonian : 4348 ± 3 Ma to 744 ± 25 Ma

Important note: This table is based only on rock and mineral ages recorded on mindat.org for this locality and is not necessarily a complete representation of the geochronology, but does give an indication of possible mineralization events relevant to this locality. As more age information is added this table may expand in the future. A break in the table simply indicates a lack of data entered here, not necessarily a break in the geologic sequence. Grey background entries are from different, related, localities.

Geologic Time				Rocks, Minerals and Events
Precambrian
	Proterozoic
		Neoproterozoic
			Tonian	ⓘ Xenotime (youngest age) 744 ± 25 Ma ⓘ Metaconglomerate (youngest age) 800 ± 25 Ma ⓘ Monazite (youngest age) 835 ± 9 Ma
		Mesoproterozoic
			Calymmian	ⓘ Zircon (youngest age) 1576 ± 22 Ma
	Archean
		Neoarchean		ⓘ Metaconglomerate (oldest age) ~2650 Ma
		Mesoarchean		ⓘ Banded iron formation 3080 ± 20 Ma Jack Hills mine, Jack Hills, Nookawarra Station, Murchison Shire, Western Australia, Australia
		Paleoarchean		ⓘ Monazite (oldest age) 3254 ± 72 Ma ⓘ Xenotime (oldest age) 3266 ± 3 Ma
	Hadean
		Basin Groups		ⓘ Zircon (oldest age) 4348 ± 3 Ma

Localities in this Region

Other Regions, Features and Areas containing this locality

References