通过对西秦岭夏河-合作地区中酸性脉岩进行锆石U-Pb年代学和全岩主微量地球化学研究，旨在揭示区域碰撞-陆内造山构造转换机制。全岩地球化学数据表明：夏河-合作地区中酸性脉岩具有高硅（59.95%~67.41%）、富钾（2.08%~3.40%）、贫钠（1.42%~2.80%）、准铝-弱过铝质（铝饱和指数A/CNK为0.77~1.17）地球化学特征，属于高钾钙碱性Ⅰ型花岗岩；稀土元素总量为128.06×10^-6~209.47×10^-6，轻稀土元素（LREE＝104.96×10^-6~182.63×10^-6）显著富集，重稀土元素（HREE＝19.91×10^-6~28.01×10^-6）明显亏损，轻重稀土元素比值（LREE/HREE＝3.92~7.73）较高。同时，岩石富集大离子亲石元素（Rb、K、Th、Li）而亏损高场强元素（Nb、Ta、P、Ti）。锆石U-Pb定年表明，夏河-合作地区中酸性脉岩形成于早三叠世晚期-中三叠世晚期［（232.4±1.4） Ma~（248.0±1.1）Ma］。结合区域地质背景，认为中酸性脉岩形成于板块碰撞导致的地壳缩短和加厚的构造背景下，经历了下地壳岩石圈发生拆沉，幔源岩浆底侵，从而导致高钾基性下地壳部分熔融，并有幔源岩浆参与成岩过程。综合区域上西秦岭西段三叠纪中酸性岩体的形成时代，推断西秦岭西段碰撞造山向陆内造山的转换时限发生在231~248 Ma。

In order to elucidate the tectonic mechanism during the transition from collisional to intra-continental orogeny, the zircon U-Pb dating and whole-rock major and trace element geochemistry of intermediate-acidic dykes in the Xiahe-Hezuo Area of the West Qinling Orogen, China, were investigated. Whole-rock geochemical data reveals that the intermediate-acidic dykes in the Xiahe-Hezuo area show high Si (59.95% ~ 67.41%), rich K (2.08% ~3.40%), low Na (1.42% ~ 2.80%), and near-aluminous to weakly peraluminous (A/CNK = 0.77 ~ 1.17) geochemical characteristics, and classified as high-K calc-alkaline I-type granites. Total rare earth element (REE) contents vary from 128.06 × 10^-6 to 209.47 × 10^-6, with significant enrichment of light REE (LREE=104.96 × 10^-6 ~ 182.63 × 10^-6) and marked depletion of heavy REE (HREE = 19.91 × 10^-6 ~ 28.01 × 10^-6), resulting in a high LREE/HREE ratio (3.92 ~ 7.73). Additionally, the dykes show enrichment of large ion lithophile elements (Rb, K, Th, Li) and depletion of high field strength elements (Nb, Ta, P, Ti). Zircon U-Pb dating indicates that the dykes formed during the Late Early to Late Middle Triassic [(232.4 ± 1.4) Ma to (248.0 ± 1.1) Ma]. Based on the regional geological setting, the intermediate-acidic dykes was indicated to form under a tectonic setting characterized by crustal shortening and thickening due to plate collision, involving underplating of mantle-derived magmas and partial melting of high-K basic lower crust, with possible contribution from mantle-derived magmas. The transition from collisional to intracontinental orogenesis in the West Qinling Orogen is proposed to have occurred between 231 Ma and 248 Ma, based on integrated geochronological data from Triassic intermediate-felsic plutons.