Why in news
A study published in Nature Geoscience on September 2 aims to explain why gold nuggets are commonly found in quartz veins in mountainous regions.
This phenomenon has been a mystery without a single convincing explanation.
Gold deposits are extremely enriched, requiring factors of 1,000 to 10,000 times the normal concentration to be economically viable, compared to base metals like copper which need about 200 times enrichment.
Orogenic gold systems, where most nuggets originate, have historically been economically significant, accounting for up to 75% of all gold mined.
‘Orogenic’ refers to large-scale geological processes that form mountains, such as tectonic plate interactions.
The study focuses on why gold nuggets are found in orogenic quartz veins, despite the fact that gold is not very soluble in fluids and conventional theories do not fully explain this.
Gold's low solubility in fluids makes it impractical to form deposits from condensed gold in water alone.
Some theorized that gold might be present as nanoparticles in water, but this doesn’t explain the deposition of large quantities of gold.
The comparison to epithermal vein deposits (formed by cooling mineral-rich fluids) does not match the characteristics of orogenic deposits.
New Hypothesis - Quartz’s Role:
Quartz, being a piezoelectric crystal, develops a voltage when squeezed or distorted.
This voltage affects the electronic properties of quartz, leading to the flow of charged particles and driving electrochemical reactions through a process known as piezocatalysis.
Piezoelectricity is the ability of certain materials to convert mechanical energy into electrical energy, or vice versa
The study suggests that seismic activity (earthquakes) squeezes quartz crystals, leading to piezocatalytic reactions that deposit gold from nearby solutions
Over time, this process accumulates gold in quartz veins, forming large nuggets.
Quartz is a hard, crystalline mineral that's made up of silicon and oxygen, the two most abundant elements on Earth.
It's the second most common mineral in the Earth's crust, after feldspar, and is found in almost all types of rock.
Quartz is known for its many uses, including:
Gemstones: Quartz is used to make gemstones like amethyst, rose quartz, citrine, and smoky quartz.
Building stone: Quartz is a main component of sandstone, which is used in construction.
Electronics: Quartz can be transformed into silicon, which is used to make solar panels, semiconductors, and electronics.
Clocks and watches: Quartz crystals are used in clocks and watches to oscillate at a precise frequency.
Quartz is chemically and physically resistant to weathering, so when quartz-bearing rocks erode, the quartz grains are concentrated in soil, rivers, and beaches.
This is why white sands in river beds and on beaches are often made up of quartz
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