Location of the Jack Hills in Australia

Jack Hills

The Jack Hills are located in the Narryer Gneiss Terrane of the Yilgarn Craton, Western Australia, and comprise an 80 km long northeast-trending belt of folded and metamorphosed supracrustal rocks. ^[1] Image File history File links JackHills_Location. ... Image File history File links JackHills_Location. ... Image File history File links Oz79_small. ... Image File history File links Oz79_small. ... The Narryer Gneiss Terrane complex is verifiably the oldest known portion of the crust on Earth. ... // The Yilgarn Craton is a huge craton which constitutes the bulk of the Western Australian land mass. ... Slogan or Nickname: Wildflower State or the Golden State Other Australian states and territories Capital Perth Government Constitutional monarchy Governor Ken Michael Premier Alan Carpenter (ALP) Federal representation  - House seats 15  - Senate seats 12 Gross State Product (2004-05)  - Product ($m)  $100,900 (4th)  - Product per capita  $50,355/person... Very tight folds. ... Metamorphism can be defined as the solid state recrystallisation of pre-existing rocks due to changes in heat and/or pressure and/or introduction of fluids i. ...

Sedimentary siliciclastic rocks, interpreted as alluvial fan-delta deposits, are the major lithology. Minor mafic/ultramafic rocks and banded iron formation (BIF) are also found in the sequence. The overall sequence is generally considered to be a granulite 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). Two types of sedimentary rock: limey shale overlaid by limestone. ... Nile River delta, as seen from Earth orbit. ... In geology, mafic minerals and rocks are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ... Ultramafic (or ultrabasic) rocks are igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). ... 2. ... Modern petrology defnes a granulite sensuo stricto as a coarse grained, high-grade metamorphic rock composed primarily of pyroxene, plagioclase feldspar and accessory garnet, oxide and amphibole. ... Figure 1. ...

Oldest zircon on Earth

Detrital zircons with ages >4000 Ma have been found in these rocks and a 4,404 +/- 8 Myr zircon was found at Eranondoo Hill ^[2], the oldest dated material on Earth; the date is in the Cryptic era of the Hadean eon. They were found within part of the 3.6-3.8Ga supracrustal sequence. These zircons are considered most likely to have been placed into these rocks by erosion of older material.^[3] Zircon is a mineral belonging to the group of nesosilicates. ... The oldest rock or rocks on Earth are from the Archean Eon and are only partially exposed on the surface. ... Cryptic era occoured from 4. ... The name Hadean refers to the geologic period before 3800 million years ago (mya). ...

The importance of this interpretation is that, in order for the rocks of the Jack Hills to contain detrital zircons, the Earth must have firstly been cool enough to support liquid water on the surface, if not a water ocean^[4]; that there must have been some kind of temporary crust, most likely very thin, on the surface of the Earth, and not a magma ocean as postulated for the earliest phase of the Earth's history. For the history of modern humans, see History of the world. ...

Economic geology

The Jack Hills banded iron formation is the site of a minor iron ore mine operated by Midwest Corporation which is exporting 3 million tonnes per annum of high grade detrital hematite iron ore via the port of Geraldton. The company plans to expand the operation to include extraction of the magnetite bearing BIF. This heap of iron ore pellets will be used in steel production. ... Hematite, also spelled haematite, is the mineral form of Iron(III) oxide, (Fe2O3), one of several iron oxides. ... Geraldton is a town in Western Australia located 424 km north of Perth. ... // Headline text Magnetite is a ferrimagnetic mineral form of iron(II,III) oxide, with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. ...

Other companies operating in the area are also planning major magnetite BIF based iron ore mines ^[5]

See also

• Iron ore
• Archean
• Hadean
• Zircon
• History of Earth
• Timetable of the Precambrian

This heap of iron ore pellets will be used in steel production. ... The Archean is a geologic eon; it is a somewhat antiquated term for the time span between 2500 million years before the present and 3800 million years before the present. ... The name Hadean refers to the geologic period before 3800 million years ago (mya). ... Zircon is a mineral belonging to the group of nesosilicates. ... For the history of modern humans, see History of the world. ... // This is a timeline of geological and relevant astronomical events on Earth before the Cambrian period started. ...

References

1. ^ Western Australia's Jack Hills. NASA Earth Observatory newsroom. Retrieved on 2006-04-28.
2. ^ AEvidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago.. Nature, v. 409, pp. 175-178. (2001). Retrieved on 2006-04-28.
3. ^ Zircons are Forever Zircons are Forever. Retrieved on 2007-04-28.
4. ^ Lindsey, Rebecca (March 1, 2006). Ancient Crystals Suggest Earlier Ocean. NASA Earth Observatory. Retrieved on 2006-04-28.
5. ^ Midwest Resources Conference 2007. Midwest Development Corporation (March 1, 2007). Retrieved on 2007-08-31.