Lithium and Nd isotopic constraints on the origin of Li-poor pegmatite with implications for Li mineralization

Chen, Bin; Huang, Chao; Zhao, Hui

2020-09-30

10.1016/j.chemgeo.2020.119769

CHEMICAL GEOLOGY   影响因子和分区

0009-2541

1872-6836

Although volumetrically minor in the upper continental crust, pegmatites host lots of rare-metal mineralization (e.g., Li, Be). Pegmatites and associated mineralization were generally thought to originate from extreme differentiation of a parent granite system. We propose an alternative model to interpret the genesis of pegmatite and factors controlling Li mineralization based on combined Nd and Li isotopic studies on the Li-poor pegmatites (barren) from the Qinghe pegmatite field of the Altai orogen (NW China). The Qinghe pegmatites show significantly varied Nd isotopic compositions (epsilon(Nd)(t) = - 4.3 similar to 1.7), which overlap the surrounding schists (- 6.5 similar to 1.5), but lower than the granites (- 2 similar to + 2.9) of the orogen. These data, together with the low REE (3.3-41 ppm) and absence of biotite in the pegmatites, suggest they were not derived from extreme differentiation of a parent granite as traditionally thought, but from low degrees of partial melting of the schists involving muscovite dehydration melting under amphibolite facies conditions. The pegmatites are characterized by heavy Li (delta Li-7 = 4.1-14.5 parts per thousand) and low Li abundance (3.6-50 ppm), which contrast to that of local schist (delta Li-7 = + 0.9 similar to + 3.0 parts per thousand, Li = 24-123 ppm) and granite (delta Li-7 = +0.9 similar to + 3.0 parts per thousand, Li = 24-70 ppm), and also to that of global Li-rich pegmatites (delta Li-7 = - 1.0 similar to +10 parts per thousand, Li > 500 ppm). Modeling study indicates that Li-poor pegmatites always have heavy Li signature compared with Li-rich pegmatites due to the abundance of biotite in the source. The formation of Li-rich pegmatite with Li mineralization is attributable to the distinct source characteristics with abundant fluxing components like Li, Na, CO32-, and HCO3- and sufficient alumina-rich clay phases, and the fluxing components probably originated from evaporate interlayers in the source.

Pegmatite PARTIAL MELTING EQUILIBRIA Lithium isotopes RARE-METAL PEGMATITES Li mineralization CHINESE ALTAI ACCRETIONARY OROGENESIS TECTONIC EVOLUTION BLACK-HILLS FRACTIONATION LEUKOGRANITE PETROGENESIS GRANITES

SCI ; EI

英语

第一 ; 通讯

National Natural Science Foundation of China[41872051]

Geochemistry & Geophysics

Geochemistry & Geophysics

WOS:000566789900006

ELSEVIER

20202908945856

Neodymium ; Alumina ; Mineralogy ; Melting ; Isotopes ; Lithium ; Aluminum oxide ; Mica

Mineralogy:482 ; Minerals:482.2 ; Lithium and Alloys:542.4 ; Rare Earth Metals:547.2 ; Alkali Metals:549.1 ; Chemical Operations:802.3 ; Inorganic Compounds:804.2

GEOSCIENCES

Web of Science

Southern Univ Sci & Technol, Dept Earth & Space Sci, Shenzhen, Peoples R China

Chen, Bin,Huang, Chao,Zhao, Hui. Lithium and Nd isotopic constraints on the origin of Li-poor pegmatite with implications for Li mineralization[J]. CHEMICAL GEOLOGY,2020,551.

Chen, Bin,Huang, Chao,&Zhao, Hui.(2020).Lithium and Nd isotopic constraints on the origin of Li-poor pegmatite with implications for Li mineralization.CHEMICAL GEOLOGY,551.

Chen, Bin,et al."Lithium and Nd isotopic constraints on the origin of Li-poor pegmatite with implications for Li mineralization".CHEMICAL GEOLOGY 551(2020).