Geochemical,Boron Isotope Characteristics and Geological Significance of Tourmaline from Tangyin Granitic Pegmatite in Yihuang,Jiangxi Province
Yuan Jing
Cao Yi
Tang Chunhua
Yan Junling
Zhou Yu
Qian Zhengjiang
Liu Xiaolong
Wang Mingyou
Sun Chao
Abstract：Granitic pegmatite is extensively developed in the Yihuang area of Jiangxi Province,and tourmaline is commonly found within granitic pegmatite and its surrounding rocks(biotite monzogranite).Three distinct types of tourmalines have been identified in Tangyin area:randomly disseminated tourmaline(Tur-G)in biotite monzogranite,unzoned tourmaline(Tur-PU)and zoned tourmaline(Tur-PZ)in granitic pegmatite.However,the classification and origin of tourmaline,as well as its implications for the genesis of granitic pegmatite,remain unclear.This study analyzed the major,trace elements,and boron isotopic compositions using EPMA and LA-(MC)-ICP-MS.From Tur-G type→Tur-PU type→Tur-PZ tourmalines core to rim,the concentrations of Al and Fe initially increase and subsequently decrease,whereas the concentrations of Mg,Na,Ca,Ti,Sc,V,Cr,Co,Ni,Sr,Ga,and rare earth elements exhibit an opposite trend,decreasing first and then increasing.The δ11B values for Tur-G,Tur-PU,Tur-PZ type tourmalines core and rim are-10.77‰--8.87‰,-10.59‰--8.73‰,-11.07‰--10.09‰,and-11.05‰--8.95‰,respectively.It is believed that all tourmalines belong to the iron-magnesium tourmaline series within the alkaline tourmaline group and are of magmatic origin.Specifically,Tur-G,Tur-PU,and Tur-PZ tourmalines crystallized during the late granite melt,the early granitic pegmatite melt,and the late magma-hydrothermal stages,respectively.The changes in the Fe3+/Fe2+ratio and V content of the tourmaline revealed that the oxygen fugacity of the magma melt exhibit a trend of initially decreasing and subsequently increasing.The concentrations of Mg,Na,Ca,Ti,Sc,V,Cr,Co,Ni,Sr,and Ga in the tourmaline reflect variations in elemental composition within the melt.The tourmaline found in both the Tangyin granitic pegmatite and biotite monzogranite exhibits a concentrated and comparable boron isotope composition,ranging from-11.07‰ to-8.73‰.This similarity suggests that both rock types originated from the same magma source,with the initial magma being derived from the partial melting of the continental crust,specifically calcium-poor and aluminum-rich metamorphic mudstone and sandstone.
Keywords：tourmalinegranitic pegmatitegeochemistryboronisotopemagmatic evolutionmagma sourceTangyinJiangxi Province
Publication Date：2025-11-30
Online Publishing Date：2025-12-15(First online date of this platform, not the publication date of the document)
Pages：17( 4442-4458 )