Geochemistry, zircon U−Pb and Hf isotopes of the high−purity pegmatite−quartz deposits in the Eastern Qinling and discussion on its prospecting direction

This paper is the result of mineral exploration engineering.

Objective As the world's scarce strategic mineral resource, high−purity quartz is the key basic material of strategic emerging industries. Spruce−Pine granitic pegmatite was used as raw material by the United States to produce high−end quartz sand products, which were better than the quality of 4N8, and almost monopolized the international market. The discovery of 4N class high−purity pegmatite−quartz deposits in Eastern Qinling provides a rare opportunity to study the formation mechanism of high purity quartz, realize prospecting breakthrough and establish metallogenic model.

Methods Based on the field investigation of the newly discovered high−purity pegmatite-quartz deposits in the Eastern Qinling Mountains, the geochemistry, zircon U−Pb isotope chronology and Hf isotope of pegmatite deposits in Spruce−Pine high−purity quartz deposits in the United States were compared.

Results The Eastern Qinling 10 high purity quartz deposit was formed in the Early Devonian with a zircon U−Pb age of (406.8±0.8) Ma, which is earlier than that of high purity quartz granite−pegmatite in Spruce−Pine. The formation temperature of pegmatite from high purity quartz deposit in Eastern Qinling and Spruce−Pine is about 600℃. Pegmatite from the high purity quartz deposit in the Eastern Qinling has similar geochemical characteristics to pegmatite from the high purity quartz deposit in Spruce−Pine, showing features of I-type granite and high differentiation evolution. The materials in the source area come from both lower crust and mantle. It is not enough to completely invert the characteristics of the source area and the diagenesis and mineralization process by compared the spatial relationship with formation age and petrogeochemical characteristics. Whether the pegmatite of high purity quartz deposits and Huichizi granite pluton in the Eastern Qinling have the homologous evolution still needs further study.

Conclusions Compared with the granite type, magmatic characteristics and formation temperature of the high−purity quartz deposits (points) in the Eastern Qinling and Spruce−Pine are similar, which provides a theoretical basis for further revealing the geological background of high−purity quartz mineralization and achieving breakthroughs in high−purity quartz ore deposits prospecting.