calcite sea and aragonite sea

When facing the sea, you can see that for hundreds of millions of years, the composition of sea water has been fluctuating between "calcite sea" and "aragonite sea".



In 1983, Professor Sandberg of the United States made such a conjecture: since the 540 million-year-old Neoproterozoic era, the main components of seawater have changed in calcite and aragonite, corresponding to the so-called "calcite sea" and "aragonite sea".

In 1983, American professors made such a conjecture: since the 540 million-year-old Neoproterozoic era, the main component of seawater is calcite, which is called "calcite sea". The other three stages are Neoproterozoic-early Cambrian, Late Carboniferous-Late Triassic, Early Jurassic and Middle Cenozoic. Period - modern, the main component of its sea water is aragonite, known as "aragonite sea".



But these are really just guesses!



How to distinguish "calcite sea" from "aragonite sea"?



The calcite sea and aragonite sea are inferred from the composition of marine abiotic crust carbonate rocks in the sea water.



The so-called "Calcite Sea" is that the minerals contained in it are mainly composed of calcite, i.e. calcium-rich ions (Ca2+) and low sulfate ions (SO42-).



It is called "aragonite sea" because the mineral composition is mainly composed of aragonite, namely magnesium-rich ion (Mg2+) and sulfate-rich ion (SO42-).



Modern sea water is a component of aragonite sea.



In short, the main elements are different. So, how to analyze the elements in ancient seawater?



Strange Seal Makes Time Flow Back



A peculiar "seal" will shine on the stage... Fluid inclusions!



The original fluid inclusions in the halite minerals (i.e. sea salt) formed by evaporation in sea water "seal" the original sea water at that time.



Scientists extract the ingredients of the original sea water (genuine "expired" sea water) and restore the ingredients of the sea water at that time.



Fluid inclusions are crystal defect voids during mineral formation, which can record fluid composition during mineral formation, such as water bladder in agate.



Research methods for fluid inclusions:



Since the 1970s, scientists in the former Soviet Union have used ultramicro-geochemical methods to extract and analyze the composition of fluid inclusions in rock salt by capillary glass tube.



In 2001, a team of American scientists used freeze scanning electron microscopy (SEM) to analyze the composition of rock salt fluid inclusions in geological period to restore the composition of seawater in geological period.



It was not until 2006 that researchers from China began to study the fluid inclusions of halite in accordance with international methods.



Why is the composition of the Ordovician seawater blank?



Since the 1970s, scientists have successively analyzed the mineral composition of seawater at various stages since the Neoproterozoic.



These results confirm Professor Sandberg's conjecture in 1983. Only the Ordovician, an important part of the geological history, remains a mystery about the composition of the sea water