Petrography, geochemistry, and geochronology of the Kohistan Batholith granitoids from the Central Kohistan Magmatic Arc, Northern Swat, Pakistan

Kohistan地形包括一个白垩纪海内弧，该弧在晚白垩世与喀喇昆仑地块碰撞后成为安第斯型边缘。在碰撞过程中，Kohistan被隆起，因此弧的一个独特完整的部分现在从基性-超基性基底到顶部的火山和花岗岩暴露出来。科希斯坦岩基构成了弧的主要单元，由一系列花岗岩类和与火山和变质岩伴生的小辉长岩和闪长岩组成。研究区位于巴基斯坦斯瓦特北部，含片麻岩石英闪长岩、闪长岩、闪长岩（闪长岩类和埃达克岩）、花岗岩、长辉长岩塞体和一小块闪长岩侵入体。这些岩石在空间上与小型火山、混染变质岩和角闪岩有关。斯瓦特山谷的详细地图和采样于2021年完成。作为该项目的一部分，将使用电子显微镜和电子探针分析对所有暴露岩石单元的岩石学特征进行详细研究。利用x射线荧光和ICP-MS分析测定不同花岗岩类及其伴生基性、火山岩和变质岩的主要和微量元素组成。锆石、磷灰石、钛矿和独居石等矿物的原位U-Pb定年将有助于阐明弧相关岩浆活动的开始，以及石英闪长岩、花岗岩、闪长岩、较年轻的浅花岗片和辉长岩塞、火山和可能较老的变质沉积物和角闪岩之间的年龄关系。锆石的原位Hf同位素将有助于确定不同火成岩套的来源，而锆石的形态和微量元素组成将允许计算其结晶温度。深成岩中角闪孔的组成将用于确定其侵位深度。虽然对Kohistan岩基东部的花岗岩类进行了一些详细的研究，但斯瓦特Kohistan北部暴露的花岗岩类的岩石学、地球化学、同位素和年龄数据大多缺失。上述所有分析技术结合测绘和解释GIS数据，将用于了解花岗岩类的岩石成因和演化，并揭示其地球动力学背景及其与伴生火山岩和变质岩的关系。

The Kohistan terrain comprises a Cretaceous intra-oceanic arc which became an Andean-type margin after collision with the Karakoram block in the Late Cretaceous. During collision, Kohistan was obducted, so a uniquely complete section of the arc is now exposed from mafic-ultramafic base to volcanic and granitic rocks at the top. The Kohistan batholith constitutes the major unit of the arc and comprises a range of granitoids and minor gabbro and diorite associated with volcanic and metamorphic rocks. The research area in Northern Swat, Pakistan, contains plutonic bodies of gneissose quartz diorite, tonalite, diorite (sanukitoids and adakites?), granite, plugs of gabbronorite, and a small diorite intrusion. These rocks are spatially associated with minor volcanics as well as migmatitic metasediments and amphibolites. The Swat valley was mapped in detail and sampled in 2021. As part of the project, the petrological characteristics of all rock units exposed will be investigated in detail, using electron microscopy and electron microprobe analysis. Major and trace element compositions of the different granitoids and the associated mafic, volcanic, and metamorphic rocks will be determined using X-ray fluorescence and ICP-MS analysis. In-situ U-Pb dating of minerals such as zircon, apatite, titanite, and monazite will help to elucidate the onset of arc-related magmatism and age relationships between quartz diorite, granite, tonalite, younger leucogranite sheets and gabbroic plugs, the volcanics and the presumably older metasediments and amphibolites. In-situ Hf isotope of zircon will help to resolve the sources of the different igneous suites, whereas the morphology and trace element composition of zircon will allow to calculate its crystallization temperatures. The composition of amphibole in the plutonic rocks will be used to determine their emplacement depths.Whilst granitoids in the eastern part of the Kohistan Batholith have been studied in some detail, petrological, geochemical, isotopic, and age data are largely missing for those exposed in northern Swat Kohistan. All the above-mentioned analytical techniques combined with mapping and interpreting GIS data will be used to understand the petrogenesis and evolution of the granitoids and to unravel their geodynamic setting and relationship to associated volcanic and metamorphic rocks.