The Jiajika pegmatite- type lithium deposit in Western Sichuan is the largest hard- rock lithium deposit in China. The “Jiajika Pegmatite- type Lithium Deposit Scientific Drilling Project ”(JSD) was conducted with the aim of revealing the deep structure and ore- forming mechanism of the pegmatite- type lithium deposit. This project involved three scientific drill boreholes: a 3211.21 m borehole (JSD- 1) and two 1000 m boreholes (JSD- 2 and JSD- 3). The following innovative research findings were obtained: ① It was discovered that the Late Triassic turbidite within the depth of 0~900 m in JSD- 1 experienced medium- to- low pressure and high- temperature Barrovian- Buchan- type metamorphism, as well as deformation related to gneiss dome formation. ② Lithium- bearing pegmatites were identified within 0~100 m depth of JSD- 1. The rare element abundances and mineralization potential in the pegmatites of the 3211 m deep borehole were estimated. ③ Precise isotopic dating of cassiterite, columbite- tantalite, and monazite reveals two magmatic- hydrothermal events (ca. 210~204 Ma and ca. 193~192 Ma) of the pegmatites in JSD- 1. ④ The enrichment of alkaline elements (Li, Na, K, Rb, Cs) and volatile elements (B, As) in fluid inclusions indicates highly fractional crystallization of the pegmatites. Li- B- Fe- Nd isotopes of JSD- 1 core samples revealed the magmatic evolution, fluid exsolution process, and ore- forming mechanism. It showed that during the magmatic evolution of the Jiajika pegmatite- type lithium deposit, magma differentiation promoted extensive fluid exsolution, leading to the formation of albite- spodumene pegmatite bodies in shallow depths, refuting the idea that the pegmatites were derived from in- situ melting of sedimentary rocks. ⑤ The study revealed the Marjinzi S- type granite body closely related to the Jiajika pegmatite lithium deposit is not a deep- seated large granite batholith, contrary to previous assumptions. Instead, it is composed of several “rootless” dome- like granitic sheets separated by multilayered metamorphic rocks and rare- element pegmatites, forming a “multi- layer sandwich” structure. This proposes a groundbreaking ore- controlling theory of “multilayered domal granitic sheets” for the Jiajika pegmatite- type lithium deposit. ⑥ The formation process of the Jiajika pegmatite- type lithium deposit during the Late- Triassic to- Early- Jurassic Cimmeria Orogeny (230~190 Ma) was outlined. It involved shear- induced melting in deep crust, magmatic ascending, forming of granitic sheets along pre- existing reverse faults (or shear zones), doming of the sheets due to magma ascent and decompression, as well as Barrovian- Buchan- type metamorphism, leading to the mineralization of the pegmatites through multiple magmatic- hydrothermal events. ⑦ Danba- type migmatization in deep crust was proposed to have provided the magma for the Jiajika granite sheets and the lithium bearing pegmatites. ⑧ Low- temperature thermochronological results from the borehole samples indicated three stages of exhumations in the Jiajika lithium deposit. The overall amount of exhumation since the mineralization (<200~190 Ma) was estimated to be 5±1 km. The lower exhumation rate of the Jiajika dome since the Cenozoic might have been a favorable condition for the preservation of the lithium deposit. ⑨ Six exploration indicators for the Jiajika- type lithium- bearing pegmatites were proposed.