Porphyry copper–gold deposits are large volume, low-grade disseminations formed by precipitation of copper and gold (plus molybdenum) from fluids of magmatic origin1. The majority of porphyry Cu–Au deposits are associated with typical calc-alkaline magmas (often high Sr/Y) in Andean-type subduction zones1.
What is porphyry ore?
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. Some mines exploit porphyry deposits that contain sufficient gold or molybdenum, but little or no copper.
What minerals are in porphyry?
In carbonate rocks, the most common minerals are garnet, pyroxene, epidote, quartz, actinolite, chlorite, biotite, calcite, dolomite, K-feldspar, and wollastonite. Other alteration minerals commonly found in porphyry copper deposits are tourmaline, andalusite, and actinolite.
What does porphyry look like?
In its non-geologic, traditional use, the term porphyry refers to the purple-red form of this stone, valued for its appearance. 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.
Is porphyry A granite?
Granite (porphyritic) 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.
Can you buy porphyry?
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Where does porphyry come from?
The word “porphyry” comes from the Latin word for purple, which was the color of nobility to the Romans. Porphyry was Imperial Rome’s most prestigious stone for columns, vases, alters, busts and other objects.
What does porphyry mean in earth science?
“Porphyry” is a diversity of igneous rock consisting of large-grained crystal such as quartz and feldspar scattered in a fine-grained groundmass.
What is the meaning of porphyry?
Definition of porphyry 1 : a rock consisting of feldspar crystals embedded in a compact dark red or purple groundmass 2 : an igneous rock of porphyritic texture
What is a porphyry copper–gold deposit?
Gold is closely associated with copper in essentially all of these deposits, as discussed more fully below. Thus, porphyry copper–gold deposits should be defined as those with bulk Cu/Au atomic ratios below 40,000, rather than the limit of about 31,000 suggested by Kirkham and Sinclair (1995).
What are the characteristics of porphyry rocks?
Most porphyry deposits occur in partially exhumed sections of continental or island arcs in subduction-zone settings, and associated igneous rocks commonly have metaluminous, calc-alkaline compositions ranging from andesite to dacite and more rarely rhyolite, the latter associated with Cu-Mo and Mo-rich ores.
What are the by-products of porphyry mining?
Porphyry mines produce more than 70% of global copper, nearly all of the molybdenum, and about 20% of the World’s gold—in addition, 80% of rhenium, nearly all tellurium, and significant silver and zinc are also produced as by-products ( Sillitoe, 2010; John and Taylor, 2016 ).
