2008-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/709696摘要：台灣位於呂宋島弧與歐亞板塊之間的碰撞聚合帶，形成連續且年輕的地體構造活動。為探討台灣北部造山帶抬升後期地殼之冷卻與其他構造運動相關之熱歷史，本研究採取台灣北部三個地區之岩石樣本進行核飛跡定年。 第一部份沿花蓮北部大南澳片岩區的和平林道採集13個不同高度的變質岩岩樣，測定後得11個磷灰石核飛跡年代，討論海拔高度與磷灰石核飛跡年代的關係。年代介於0.7±0.1Ma與0.3±0.1Ma之間，表示在0.7Ma之後，此區磷灰石核飛跡受到熱作用而癒合。岩樣的磷灰石核飛跡年代與海拔高度沒有良好正相關性，與前人磷灰石核飛跡年代所顯示的結果相近，推測這些樣本因該地的等地溫線以及地下熱源分佈不均、剝蝕速率各地不一致等原因，造成核飛跡年代的差異。 以假設地溫梯度與封存溫度來估算，剝蝕速率介於3-9mm/yr（0.7Ma以來），冷卻速率為225-540°C/m.y.，顯示大南澳片岩區北部正處於高速抬升與剝蝕的狀態之下。 第二區採取雪山山脈北段之砂岩與變質砂岩標本進行磷灰石核飛跡定年完成6個數據組。標本之磷灰石核飛跡皆受蓬萊造山運動影響而完全癒合，雪山山脈北段有愈北、愈西邊磷灰石核飛跡年代愈老的趨勢，其年代介於0.6Ma ~ 4.6Ma之間。此區地殼之剝蝕速率為0.66 ~ 4.64 mm/yr，有愈晚期速率愈高的趨勢，與中央山脈相比則較為緩慢，不過進入第四紀晚期剝蝕速率減慢，可能與琉球島弧隱沒作用的西侵，使得北部山脈應力由壓縮轉為伸張，進而下陷產生正斷層有關。 第三研究區則利用觀音火山西南方林口台地的一口鑽井，採取林口礫石層上部約~100公尺內的十個沉積物岩芯，分離出鋯石測定核飛跡年代，以探討林口礫石層的沉積年代及台灣北部的古剝蝕/冷卻速率。本研究測得鋯石顆粒年代的範圍介於0.9 ± 0.6 ~ 245.6 ± 201.7 (1σ) Ma.。可區分出林口礫石層鋯石顆粒年代分別代表三個來源區的冷卻或生成年代：屬於在火成岩來源區的鋯石顆粒核飛跡年代介於2.6 ± 0.4 ~ 0.9 ± 0.6 (1σ) Ma。推論台北盆地因山腳正斷層活動而陷落，以致於古新店溪不再提供沉積物堆積至林口沖積扇的年代約為~0.9 ± 0.6 (1σ) Ma；核飛跡年代介於4.1 ± 0.9 ~ 90.8 ± 18.4 (1σ) Ma的鋯石顆粒研判來自雪山山脈，核飛跡年代反應鋯石經歷不同程度的熱作用而部分癒合或全部癒合；來自西部麓山帶的鋯石，核飛跡年代介於91.5 ± 1.1 ~ 245.6 ± 201.7 (1σ) Ma之間，其中又以110 ~ 160 Ma為主，與前人研究結果大致符合，進一步證實西部麓山帶沉積物源自於大陸東南白堊紀燕山晚期的岩石為主 <br> Abstract: In order to further understand the thermo-tectonic implication of the Taiwan mountain belt, a plenty of samples were collected from three different geological transects for zircon/apatite fission track dating. The first one is along the Hopin trail in the Tananao Schist terrain. Eleven rock samples at different elevation were collected for apatite fission track dating. The mean age obtained for individual rock sample ranges from 0.3±0.1Ma to 0.7±0.1Ma. No positive correlation between the mean apatite fission-track ages for the rock samples and their elevations were found, implying non-parallel isotherm due to high topographic relief and rapid uplift rate. The second sampling transect is located in the northern part of the Hsuehshan Range. Six apatite fission track ages were determined for the sandstone and meta-sandstone samples. Mean apatite fission track ages for individual rock sample range from 0.6±0.1 to 4.6±0.7 Ma. The apatite fission track ages are older in the northern and western part of the north Hsuehshan Range. The detrital zircon grain FT ages of the Linkou Gravel Formation span widely from 0.9 to over ~190 Ma, suggesting that the detrital zircons of the formation were not annealed after deposition. Each rock sample shows 2-3 groups in the grain age distribution, implying that the Linkou Formation have multiple provenance. Of which, the youngest group ranges from 2.6±0.9 to 0.9±0.4 (1σ) Ma, suggesting the maximum depositional age of the uppermost 100m-thick layer of the Linkou Gravel Formation is about 0.9±0.4 (1σ) Ma, which is close to its depositional age. The second group of zircon grain ages spans from 4.1±0.8Ma to 90.8±16.6Ma (1σ), and is considered as derived from the northern Hsuehshan Range. The zircon FT ages of the third group range from 91.5±22.5 to 192.6±25.0 (1σ) Ma, reflecting a sediment source from the unmetamorphosed Western Foothills.磷灰石鋯石核飛跡剝蝕速率中央山脈雪山山脈大南澳片岩林口台地。ApatiteZirconFission TrackExhumation rateCentral RangeHsuehshan RangeTananao SchistLinkou Tableland.