Geology of the Mutis Complex, Miomaffo, West Timor

Mesozoic forearc assemblages are widespread across Indonesia, and these are also exposed in the overthrust terranes on Timor. The oldest rocks in the allochthonous Mutis Complex, West Timor are Mesozoic basaltic volcaniclastic rocks and melange containing blocks of normal mid-ocean ridge basalt (N-MORB) basalt (194 ± 5 Ma), amphibolite (metamorphism at 184 ± 6 Ma), garnet and actinolite-bearing schists, arkosic sandstone and volcanogenic sedimentary rocks. Based on the large component of Jurassic material, these rocks were probably derived from the Woyla terrane. The eastern part of the Miomaffo massif is complexly deformed with a dominant foliation overprinted by several fold and fault events including late normal cataclastic zones. This sequence is intruded by calc-alkaline andesitic dykes (possibly in the Eocene). The Central Sector of the massif is a block of high-strain greenschist facies rocks where the primary texture can no longer be recognised, but the bulk composition is the same as the volcaniclastic rocks in the east. Further west is an amphibolite facies metamorphic province. Amphibolite from the Western Sector have the same N-MORB composition as the basalt in the east, but the gneissic rocks have a higher proportion of arc-sourced protoliths. The peak metamorphic conditions were 650 °C and 0.9 GPa. This metamorphic event occurred at 37 Ma, reflecting subduction on the southeast margin of Sundaland, whereas the low-grade Mesozoic metamorphism of the Eastern Sector of the massif occurred in the accretionary prism along the Woyla Arc. The Mutis Complex at Miomaffo demonstrates the complex geological history of Mesozoic rocks in eastern Indonesia. The Miomaffo massif demonstrates the strong oceanic character of the Banda terrane. The anomalous Eocene metamorphic age of rocks ‘unconformably overlain’ by Cretaceous sediments is resolved.中生代弧前组合广泛分布于印度尼西亚境内，同时也出露于帝汶岛的逆冲地体中。西帝汶异地体穆蒂斯杂岩（Mutis Complex）中最古老的岩石为中生代玄武质火山碎屑岩及混杂岩，其中包含正常洋中脊玄武岩（N-MORB）块体（194±5 Ma）、角闪岩（变质时代184±6 Ma）、含石榴子石与阳起石的片岩、长石砂岩及火山成因沉积岩。基于其中侏罗纪物质占比极高，这套岩石可能源自沃利亚地体（Woyla terrane）。 米奥马福地块（Miomaffo massif）东部构造变形复杂，主体面理被多期褶皱与断裂事件叠加改造，其中包括晚期正断层碎裂岩带。该序列被钙碱性安山岩脉侵入（可能形成于始新世）。地块中部为高应变绿片岩相岩石块体，原生结构已无法识别，但整体化学成分与东部的火山碎屑岩一致。地块西侧则为角闪岩相变质带。西部的角闪岩与东部的玄武岩具有相同的N-MORB成分，但片麻岩原岩的弧源组分占比更高。其峰期变质条件为650 ℃、0.9 GPa，该变质事件发生于37 Ma，反映了巽他地块（Sundaland）东南缘的俯冲作用；而地块东部的低级别中生代变质作用则发生于沃利亚弧（Woyla Arc）沿线的增生楔中。米奥马福地块的穆蒂斯杂岩展现了印度尼西亚东部中生代岩石复杂的地质演化历史。 米奥马福地块佐证了班达地体（Banda terrane）极强的大洋属性。 此前被认为“不整合覆盖于”白垩纪沉积物之上的岩石，其异常始新世变质时代已得到厘清。