富闪深成岩的成因及其地球动力学意义

富闪深成岩是一套以角闪石为标志矿物的侵入杂岩,可由角闪石岩、角闪辉长岩、角闪闪长岩、(英云)闪长岩、黑云母花岗岩等不同酸度系列的岩石组成。在元素地球化学方面,富闪深成岩可呈低钾拉斑质、钙碱性或钾玄质,富集大离子亲石元素和轻稀土元素。起源于经俯冲作用改造的岩石圈地幔或软流圈地幔部分熔融的基性母岩浆通过分离结晶、同化-混染,或与壳源岩浆混合,形成富闪深成岩系列中不同的岩性端元。高水含量作为富闪岩浆体系的基本特征不仅塑造了杂岩体的标志性角闪石矿物学特征,也主导了岩浆的钙碱性演化趋势。富闪杂岩形成环境相对特殊,通常产于板块会聚终末期的洋脊-海沟交互场景和后碰撞阶段,并受到同时期区域构造作用控制。基于野外产出上的共生性和地球化学的相似性,富闪深成岩与高Ba-Sr花岗岩、晚太古代赞岐岩类存在密切的成因关联,对其进行类比研究,不仅有助于富闪深成岩成因解析,也可为探讨大陆地壳生长-分异机制及地球早期构造体制提供崭新视角。最后,作为显生宙克拉通早期破坏过程的重要岩浆记录,华北克拉通北缘发育的多期晚古生代富闪深成杂岩有望为揭开富闪深成岩成因和地球动力学奥秘提供重要的野外实验室。

Petrogenesis and geodynamic implications of appinite suite

The appinite suite is a group of hornblende-rich intrusive rocks, which display a lithological compositional range from ultramafic to felsic and can be composed of hornblendite, hornblende gabbro, hornblende diorite, tonalite and biotite granite. With regard to elemental geochemistry, the appinites show a low-K tholeiitic, calc-alkaline or shoshonitic affinity, with enrichment in large ion lithosphere element and light rare earth element. The appinitic parental magmas generally originate from partial melting of subcontinental lithospheric or asthenospheric mantle modified by oceanic-slab subduction. These pristine mafic magmas then undergo fractional crystallization, crustal assimilation or mixing with crustal melts, and form different endmembers of the appinite suite. As is typical for appinitic magmas, it is water that not only determined its amphibole-dominated mineralogical character, but also shaped its calc-alkaline geochemical affinity. From the perspective of geodynamic and structural constraints, the appinite suites are usually considered to be related to the ridge-trench interaction or post-collisional geodynamic process. Meanwhile, they show a close spatial/temporal and genetic connection with regional tectonism. Based on the field co-existence and geochemical similarity, the appinite suites have a close petrogenetic relationship with high-Ba-Sr granites and Late Archean sanukitoids. The systematic research on these analogues not only contributes to the study of appinite genesis, but also helps to decipher the continental crustal growth and differentiation, as well as the tectonic regime in the early history of the Earth. The last but not the least, numerous Late Paleozoic appinitic complexes from the northern margin of North China Craton should be incorporated into the new backup research proposal.