台灣的板岩帶廣泛於台灣山脈帶西翼至脊部出露，是台灣造山帶的重要組成部分。由於板岩帶是由第三紀堆積於中國大陸邊緣的沉積物所變質而來，這些岩石不曾受過中新世末期以來、活躍至今的蓬萊造山運動之前的其他造山與構造活動，因而是探討台灣造山帶演育歷史的最佳對象。針對台灣造山帶的生長模式在地學界長期有著不同的看法而形成不同的造山模型，特別是底脫斷層恆定的薄皮逆衝理論、構造底部加積、以及岩石圈碰撞模型等，各模式對山脈中物質的岩石循環-溫壓歷史之推估截然不同，成為評估各造山模型在台灣適用性的關鍵問題。相較於受到中生代古太平洋板塊隱沒作用的大南澳變質基盤雜岩，板岩帶的熱歷史可不受干擾的記錄蓬萊造山運動造成的岩石循環。本研究將運用新穎的碳質物拉曼光譜地質溫度計(RSCM)量測台灣板岩帶變質沉積岩中所夾碳質碎屑的石墨化程度推估該板岩之最高變質溫度，結合地層、構造、古地理等野外資料收集與量測及文獻整合，重建板岩帶岩石的溫壓歷史，以及其所代表之造山帶生長模式。在熱歷史有良好控制、同時有較大顆粒同構造(含鉀)礦物生長的露頭與樣本，進行原位雷射氬氬定年分析，將前述構造作用的發生時間、及其作用時間尺度解析。本計畫之工作，規劃第一年進行實驗室建構與台灣北部地區板岩帶的熱歷史調查、樣本採集與分析，第二年則在台灣中部雪山山脈南段地區進行，第三年集中於板岩帶內雪山山脈與脊樑山脈間的地質界線調查分析，第四年則嘗試將前三年調查採樣路線之間的空白區進行採樣分析，並整合四年整體成果。 ;The slate terrain is the main constituent of the Taiwan mountain belt and crops out extensively on its western flank and crest. The rocks of the slate terrain are metamorphosed Tertiary sediments deposited on the Chinese continental margin, devoid of effects from orogenic events in the Mesozoic, therefore they are best suited to studying the evolution of the current late-Cenozoic Penglai orogeny of Taiwan. Numerous hypotheses on the growth and development of the Taiwanese orogenic wedge have been proposed leading to contrasting mountain building models, notably the thin-skinned classic wedge model with a constant detachments fault, the complex wedge model with significant basal accretion, and the lithospheric collision model; each of the models has its own prediction on particle paths through the wedge, hence different rock P-T (pressure-time) histories. Quantitative documentation of slate belt rock history thus serves to be the key in discriminating the validity of the above models to the Taiwan mountain belt. This study employs the novel RSCM (raman spectroscopy of carbonaceous material) geothermometer to quantify the peak temperature/metamorphic state through measuring the graphitization degree of the organic detritus within the metasediments, then reconstruct the rock history by integrating field geologic and structural data alongside stratigraphic information and thermochronological data. The competing mountain building models will be verified against the resultant rock cycle documentations. In-situ 40Ar/ 39Ar microprobe dating will be carried out on rocks with well-constrained thermal history as above and with large K-bearing syn-kinematic mineral growths, to place crucial information on timing and time scales in the established rock P-T histories. 4 years of works has been preliminarily anticipated, with the first year on establishing the laboratory and on thermal metamorphic investigation in the northern part of the slate terrain; during the second year the slate terrain in central Taiwan will be investigated; for the third year focus will be placed on the boundary between the Hsuehshan and Backbone ranges to inspect the nature of the inter-range contact; in the fourth year the intervening regions between the surveyed route of the previous three years will be investigated, and sums up the results of the whole four years.
