高喜马拉雅结晶岩系和北喜马拉雅穹隆都发育高角闪岩相—麻粒岩相变泥质岩,岩石组合以富铝质片麻岩类为主,伴生钾质花岗片麻岩、大理岩及基性麻粒岩等。元素地球化学特征表明,其原岩主要为较富铝的长石质砂岩和石英岩质砂岩及少量粘土岩,形成于大陆边缘浅海相沉积环境。这些变泥质岩具有相似的微量元素和稀土元素地球化学特征,表现为大离子亲石元素相对高场强元素较富集,轻稀土较重稀土富集,稀土总量较高,具有较显著的 Eu 负异常。在变质矿物组合、元素地球化学特征及锆石组成等特征上,它们与青藏高原北缘的康西瓦和阿尔金孔兹岩系相似,可能是来源于冈瓦纳大陆边缘的同一套岩石。
Two types of quartzofeldspathic inclusions hosted by omphacite and garnet were identified in the Sulu UHP eclogites. The first consists of albite, quartz, and various amounts of K-feldspar. In contrast, the second consists predominantly of K-feldspar and quartz without any albite. The presence of quart-zofeldspathic inclusions within the UHP mafic eclogites indicates that partial melting occurred in deeply subducted continental crust via mica dehydration melting reactions at an early stage of rapid exhumation. Such a melting event generated hydrous Na-K-Al-Si melts. These melts infiltrated into the mafic eclogite and were captured by recrystallizing garnet or omphacite, which together followed by dehydration and crystallization to form feldspar-bearing polyphase inclusions. Formation of silicate melts within the deeply subducted continental slab not only provides an excellent medium to transport both mobile (LILE) and immobile (HFSE) elements over a large distance, but also induces effective changes in the physical properties of the UHP slab. This process could be a major factor that enhances rapid exhumation of a deeply subducted continental slab.
