The Lhasa terrane is widely regarded as an integral unit that separated from Gondwana in the Carboniferous or late Triassic, but this terrane may more reasonably consist of two subterranes that separated from Gondwana at different times. Here, we describe newly identified early Carboniferous (355–344 Ma) basic and intermediate intrusive rocks in the Xiongcun area, southern Tibet. The basic rocks that yield negative whole‐rock ε_Nd(t) values (−5.04 to −2.94) and zircon ε_Hf(t) values (−9.2 to −1.7), combined with the chemical compositions, indicate that the magmas were derived by the partial melting of an enriched lithospheric mantle in a back‐arc extensional setting. The intermediate rocks yield ε_Nd(t) and ε_Hf(t) values of −5.78 to −5.36 and −9.2 to −4.5, respectively, which suggests that they were likely produced via crust‐mantle mixing. By combining our results with those of previous studies on the Lhasa terrane, we consider that a broad back‐arc rift system, including northern and southern branches, developed along the northern margin of Gondwana under the southward subduction of the Paleo‐Tethys oceanic lithosphere during the early Carboniferous. The northern branch evolved into the Sumdo Paleo‐Tethys Ocean, which led to the separation of the North Lhasa terrane from northern Gondwana during the late Carboniferous. The subsequent northward subduction of the Sumdo Paleo‐Tethys oceanic lithosphere beneath the North Lhasa terrane during the early to middle Permian may have triggered the southern branch to further evolve into the Neo‐Tethys Ocean and eventually may have resulted in the South Lhasa terrane separating from Gondwana.

松树南沟金矿区位于北祁连成矿带中部,目前发现有东、西两个矿床,金资源量分别达中型和大型规模。尽管其为青海北祁连成矿带上的重要金矿床,但其研究极为薄弱,矿床地质特征不清,矿床成因类型存在较大争议,严重阻碍了矿区下一步矿产勘查工作部署和找矿突破。为了查明松树南沟矿区东、西矿床的地质特征及矿床成因类型,指导矿区勘查工作部署,本研究在野外地质调查和岩心精细编录的基础上,进行了系统岩矿鉴定和能谱分析。研究表明:西矿床主要赋存于晚奥陶世石英闪长斑岩及其接触带附近的上奥陶统扣门子组玄武安山岩中,蚀变类型为钾化、青磐岩化和绢云母-绿泥石化,金矿化主要产于钾化和青磐岩化蚀变带中;金属矿物主要为黄铜矿、斑铜矿、自然金、磁铁矿、黄铁矿以及少量方铅矿、闪锌矿、辉钼矿、黝铜矿,金主要以自然金的形式赋存于石英-黄铜矿-斑铜矿脉中,少部分以不可见金的形式赋存于黄铁矿中;西矿床的地质特征表明其属于斑岩型金矿床。东矿床主要产出于上奥陶统扣门子组晶屑凝灰岩、流纹质凝灰岩与玄武安山岩中,围岩蚀变主要为绢云母-绿泥石化,局部发育绢英岩化;金属矿物主要包括方铅矿、低铁闪锌矿、黝铜矿、砷黝铜矿、黄铜矿、黄铁矿、自然金及少量银金矿,金主要以自然金和少量银金矿的形式产于碳酸盐-石英-多金属脉中,少部分产于碳酸盐-石英-黄铁矿脉中;东矿床的地质特征表明其属于中硫化型浅成低温热液金矿床。结合上述地质特征和已有的地质年代学结果,本文认为东、西矿床构成一个晚奥陶世(~455Ma)斑岩-中硫化型浅成低温热液金成矿系统,其形成与原特提斯洋北向俯冲作用诱发的岩浆活动密切相关,是目前特提斯成矿域发现的最古老的斑岩-浅成低温热液成矿系统。这一认识为在北祁连成矿带乃至整个特提斯成矿域寻找与原特提斯洋俯冲作用相关的斑岩-浅成低温热液型矿床提供了重要的找矿方向,有助于深化对区域成矿规律和古生代斑岩成矿作用的认识,也为矿区和区域下一步斑岩-浅成低温热液型矿床的找矿勘查工作部署提供了重要的理论指导。