Study On Mineralogy Characteristics Of Glauberite In Qaidam Basin

Glauberite is a mineral with potential ornamental value.It belongs to sulfate celestite,and has a petal-like section similar to chrysanthemum stone.It is expected to become a new ornamental stone species.The formation of Glauberite salt is related to the storage of oil and gas resources and the enrichment of potassium salts.At the same time,it is also a carrier to record the evolution of salt lakes.The domestic research about evaporated salt mainly focuses on gypsum,magnesia,rock salt,etc.There are few reports on the geochemical element characteristics and spectroscopic characteristics of glauberite.In this paper,glauberite in the core of SG-1 borehole in the Qaidam Basin is selected as samples.The conventional gemological instruments,X-ray diffractometer(XRD),scanning electron microscope(SEM),and inductively coupled plasma mass spectrometer(ICP-MS),Fourier Infrared Spectrometer(IR),Confocal Raman Microscope and other large instruments are used to study its mineralogical characteristics,geochemical characteristics and spectroscopic characteristics.We also discussed the relationship between the morphology and genesis of Glauberite.The main results of the paper are as follows:(1)Glauberite salt is white and colorless,translucent to opaque.It crystallizes in the form of flakes or plate-shaped single crystals,with the cross-section of the aggregate being a petal-like or bamboo-leaf-like shape.The refractive index is about 1.500-1.510,and the birefringence is about0.020.The Mohs hardness is 3.6 and the specific gravity is 2.83.The unit cell parameters are a=1.0032-1.1990 nm,b=0.8033-1.1842 nm,c=0.8470-0.9941 nm,?=112.2-112.8°.(2)The content of Na⁺,Ca²⁺,Mg²⁺,K⁺,SO₄^2-,and Cl^-in the sample at 121 m of the core is16.37%,10.58%,1.568%,0.183%,61.2%,and 1.63%,respectively.The trace elements of the334 m sample are related to the depositional environment:U/Th ratio is greater than 1.25,V/(V+Ni)ratio is lower than 0.46,they indicate an oxygen-poor deposition environment;V/Cr ratio is less than 1.05,Ni/Co ratio is less than 5,V/Sc ratio is less than 9.1,they indicate Oxidized deposition environment.The ratio of Sr/Cu is greater than 10,and the ratio of Rb/Sr is0.08,which means Glauberite salt is formed in a dry environment.(3)The infrared spectrum of Glauberite salt has a strong peak at 1210-1025 cm^-1,and a weaker peak at 700-600 cm^-1,which can be classified into the characteristics anti-symmetric stretching vibration and asymmetric variable-angle vibration of sulfate groups.In the Raman spectrum,sharp peaks can be observed at 1141 cm^-1,1003 cm^-1,645 cm^-1,and 470 cm^-1.The peak of 1141 cm^-1 belongs to the antisymmetric vibration.At the same time,its appearance is related to the decrease in the symmetry of sulfate anion.The peak within 900 to 1200 cm^-1ascribed to the stretching vibration;the vibration of 645 cm^-1 can be attributed to the asymmetric variable-angle vibration.The 470 cm^-1 vibration can be assigned to the symmetrical variable-angle vibration.(4)By analyzing and comparing the test results and data of glauberite in the Qaidam Basin and different producing areas,we deduced that both primary and secondary glauberite are produced,and the distribution characteristics of glauberite are also related to the evolution of the paleolake evolution and repeated climate change.