喀喇崑崙斷層系統

喀喇崑崙斷層喜馬拉雅區域一套斜滑斷層系統。沿着斷層的滑動加速了喜馬拉雅山弧的放射狀擴張、[2]帕米爾高原的向北縮進[3]:369–378青藏高原的向東擠壓。[4][5]:428–447以目前的板塊運動計算,印度洋板塊歐亞板塊的匯聚在喜馬拉雅-帕米爾地區西部可達44±5mm/年,東喜馬拉雅地區達50±2mm/年。[6]:425–478

印度和喜馬拉雅區域的地形圖,喀喇崑崙斷層疊加於其上。喀喇崑崙覆蓋層修改自[1]

起源 編輯

喀喇崑崙斷層起源於特提斯洋的閉合。喀喇崑崙斷層自身並非板塊邊界,不過在與印度河-雅魯藏布江縫合帶相連的地方可能是。[4]:171–186鏈接帕米爾高原現存的逆沖斷層,可以推斷原始的逆沖斷層出現於17至20 Ma。

演化 編輯

喀喇崑崙斷層是右側滑斷層,大約於20 Ma開始錯動。在約14 Ma時變成以普通斷層為主導。這一結論由氬氬測年法的結果推出。[7]:1–26到10-11 Ma,喀喇崑崙斷層變成了以反張力作用為主,並向西南延伸進西藏。西南端的延伸可以從今日的岡仁波齊峰周邊活躍的南岡仁波齊沖斷層觀察到。[7][1]:451–454

長度 編輯

 
喀喇崑崙斷層相關信息,修正自[1][8]:307–326[9][10]併疊加於地形圖上。EPM=東帕米爾山脈

基於中喀喇崑崙地區的地圖,[11]:47–73[12]:603–606[13]:358[14]:65–82一般認為有一塊晚白堊世-始新世花崗岩岩磐沿喀喇崑崙斷層向右偏轉了1000km,[15]:15085–15117地理位置在西藏南部和拉達克-贊斯卡附近。[16]:923–936部分學者認為這將不同岩磐的花崗岩聯繫到一起,是不正確的。[4]另一些學者則運用鈾鉛測年法發現自23 Ma以來其右緣滑動了600km,這個過程很可能從34 Ma就開始了。這個模型中的滑動已經轉移到印度河-雅魯藏布江縫合帶和大型香腸構造中。[17]:255–2691990年代初的研究發現這一滑動還轉移到藏南脫頂斷層中。[18]:587–598根據崑崙岩磐晚古生代花崗岩,喀喇崑崙斷層滑動了至少500km。[15]大部分學者傾向於認同動得最少的假說。測量斷層沿斷層面滑動的距離受到的最大限制,是決定什麼地方屬於真正的斷層,以及哪條斷層是獨立的。現在有些學者認為喀喇崑崙斷層將於岡仁波齊峰附近轉化為印度河-雅魯藏布江縫合帶的一部分,[4]另外一些學者則將位於斷層東南部的納木那尼脫頂斷層也納入斷層本身。[5]

西北部分 編輯

喀喇崑崙斷層的西北部的爭議遠比其他區域少。它最遠延伸到塔吉克斯坦新疆邊境帕米爾高原的Miuji盆地。喀喇崑崙斷層西北部以普通斷層運動和右旋走滑位錯為主。[4]按阿基爾組的岩石看,這一地區的滑動約有150km,阿基爾組具有含化石碳酸鹽岩層。在進入帕米爾地區前,喀喇崑崙斷層是兩個分離的斷層,分別是喀喇崑崙斷層自身,和Achiehkopai斷層。[10]

東南部分 編輯

大多數人都同意斷層的東南部併入並與西藏西南部的印度河縫合帶平行。從印度河和南岡仁波齊斷層的偏移來看,喀喇崑崙斷層的南部只有120km的右旋是明顯的,[1]這一區域的張力幾乎完全反映於印度河縫合帶南緣的喜馬拉雅山脈南北向的收縮。[4]西藏西部,位於北部的約1km寬的包含鏟式正斷層的斷層區域內的新近紀噶爾盆地也承受了喀喇崑崙斷層的滑動。[9]:926–945納木那尼斷層系統在南端和喀喇崑崙斷層系統連為一體,這使得其南端有約36km寬。[19]:21–34沿緩角度正斷層——納木那尼脫頂斷層的發掘可以觀察到,斷層已經包含了36至66km的滑動。[5]

另見 編輯

參考 編輯

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