To investigate the behavior of Li isotopes during magmatic differentiation and the petrogenesis of Cu-bearing ore deposits, a suite of post-collisional adakitic rocks from Qulong region, southern Tibet, was studied. Their lithologies range from diorite through granodiorite to granite porphyry with the latter containing giant Cu deposits. Detailed evidence of field observation and geochemical signature suggest that these three sets of rocks were most likely formed by various degrees of partial melting and fractional crystallization from the same source. The dioritic enclave, granodiorite and granite porphyry have δ⁷Li values ranging from 0.2 to 8.2‰, 3.1 to 6.8‰, and 3.9 to 7.4‰, respectively. Most of these samples are overlapping in Li isotope composition, comparable to other granitoids worldwide, indicating insignificant Li isotope fractionation during partial melting and magma differentiation in adakite-like rocks. By contrast, their Li concentrations are mainly controlled by fractional crystallization as suggested from different modal mineralogy. This process does not lead to further enrichment of Cu although they have initial high concentrations (an average of ∼104 ppm). In comparison, granite porphyry has extremely high Cu contents (up to 2000 ppm) and their δ⁷Li values are positively correlated with Cu content, suggesting the involvement of magmatic fluids that most likely exsolved from deep magma chamber. Such fluids not only modified the Li isotopic compositions of granite porphyries, but also extracted metal elements from the highly evolved magma, eventually resulting in the Cu mineralization. Our work here provides new insight into the formation and evolution of the porphyry Cu-bearing deposit.

为了研究Li同位素在岩浆分异过程中的行为和含铜矿床的成因，研究了藏南曲龙地区的一套后碰撞埃达克质岩石。它们的岩性范围从闪长岩到花岗闪长岩到花岗斑岩，后者含有巨大的铜矿床。实地观察和地球化学特征的详细证据表明，这三组岩石很可能是由同一来源的不同程度的部分熔融和分级结晶形成的。闪长岩飞地、花岗闪长岩和花岗斑岩具有δ ⁷Li值分别为0.2～8.2‰、3.1～6.8‰、3.9～7.4‰。这些样品中的大多数锂同位素组成重叠，与世界范围内的其他花岗岩类相当，表明在埃达克岩样岩石的部分熔融和岩浆分异过程中锂同位素分馏不明显。相比之下，它们的锂浓度主要受不同模式矿物学所建议的分级结晶控制。该过程不会导致 Cu 的进一步富集，尽管它们具有初始高浓度（平均约为 104 ppm）。相比之下，花岗斑岩具有极高的铜含量（高达 2000 ppm）和它们的 δ ⁷Li值与Cu含量呈正相关，表明最有可能从深部岩浆房中溶出的岩浆流体的参与。这种流体不仅改变了花岗斑岩的锂同位素组成，而且还从高度演化的岩浆中提取了金属元素，最终导致铜矿化。我们在这里的工作为斑岩型含铜矿床的形成和演化提供了新的见解。