How are porphyry deposits formed?
Porphyry deposits typically form in oceanic or continental arcs above subduction zones (Fig. 1). As the oceanic plate and overlying sediment subduct, increasing pressures expel water from the sediment, and hydrous minerals in the oceanic plate start to break down.
Where can porphyry be found?
Porphyries are most commonly found along the west coast of North and South America, as well as in the Southwest Pacific. Porphyries are formed in tectonic plate convergent zones where oceanic crust has subducted beneath the continental crust, and in some cases the oceanic crust.
What is a porphyry gold deposit?
Porphyry deposits are natural suppliers of most copper and significant gold to our society. Cu tonnage plots (Cu-rich and Au-rich). Metal endowments for both trends grow larger the longer the mineralization process. However, Au is precipitated at much higher rates in Au-rich than in Cu-rich porphyry deposits.
Where are porphyry copper deposits found?
Porphyry copper deposits form in continental magmatic arcs along convergent plate-margin boundaries or in island-arc environments. The deposits are associated with subduction-related volcanic centers, although in some examples, they are thought to be associated with postcollisional volcanism.
What is porphyry used for?
Porphyry is prized for its great compressive strength and exceptional durability. For this reason it is now most commonly used as a paving stone.
What causes porphyry?
Porphyritic rocks are a product of igneous differentiation, and are generally formed when a column of rising magma is cooled in two stages: In the first stage, the magma is cooled slowly deep in the crust, creating the large crystal grains, with a diameter of 2mm or more.
Is porphyry A granite?
In terms of its mineral content this is a typical granite, consisting of pink potassium feldspar, cream sodium feldspar (plagioclase), grey quartz and black biotite mica. This texture, of large well-formed crystals in a finer matrix, is called porphyritic. …
What is a porphyry and what does it represent?
Porphyry (/ˈpɔːrfəri/ POR-fə-ree) is a textural term for an igneous rock consisting of coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate rich, generally aphanitic matrix or groundmass. The larger crystals are called phenocrysts.
Is porphyry A rare stone?
Imperial Porphyry is arguably the rarest and most historically important stone in the world. It comes from only one source; a single mountain in Egypt that the Romans called Mons Porphyry. It is a purple, volcanic stone, very dense and fine-grained, with small white inclusions.
How do you identify porphyry?
Its chief characteristic is a large difference in size between the tiny matrix crystals and the much larger phenocrysts. Porphyries may be aphanites or phanerites, that is, the groundmass may have microscopic crystals as in basalt, or crystals easily distinguishable with the eye, as in granite.
Can you buy porphyry?
Your exclusive source for the stone of emperors! Visit our store to buy Imperial Porphyry for your collection, or browse to learn more about this fascinating stone and its rich history. …
How much does porphyry cost?
Unlike permeable gravel beds, porphyry surfaces require little maintenance. Cons: Porphyry is not available in large slabs; 4 to 6 inch squares are typical, and the biggest pieces, mostly from Argentine quarries, are about 16-inches square. Price: About $7-$8 per square foot. Resources: www.milestoneimports.com.
What is a porphyry copper deposit?
Porphyry copper deposits are copper ore bodies that are formed from hydrothermal fluids that originate from a voluminous magma chamber several kilometers below the deposit itself. Predating or associated with those fluids are vertical dikes of porphyritic intrusive rocks from which this deposit type derives its name.
What are porphyry-type mineral deposits?
Porphyry-type mineral deposits result when large amounts of hot water that carry small amounts of metals pass through permeable rocks and deposit the metals. Alteration Strong alteration zones develop in and around granitic rocks with related porphyry deposits.
What is Porphyry in geography?
The term ‘porphyry’ is also used for a mineral deposit known as copper porphyry. The different stages of cooling that create porphyritic textures in intrusive and hypabyssal porphyritic rocks also lead to a separation of dissolved metals into distinct zones.
What is a hot water porphyry deposit?
Porphyry-type mineral deposits result when large amounts of hot water that carry small amounts of metals pass through permeable rocks and deposit the metals. Strong alteration zones develop in and around granitic rocks with related porphyry deposits.