台灣中部橫貫公路大禹嶺地區石英脈發育之研究

A Study of the Development of Quartz Veins in Tayuling Area, Central Cross-Island Highway, Taiwan

廖珙含(Gong-Han Liao)

指導教授 ： 羅 偉

國立臺北科技大學/工程學院/資源工程研究所/碩士(2011年)

摘要

岩石受力產生裂隙，而含二氧化矽之流體進入裂隙，並隨當時的最小主應力方向快速結晶形成石英脈，因此石英脈的形態與結晶纖維的生長方向常是了解岩體變形過程的指標。本研究以中部橫貫公路大禹嶺地區沿線出露之石英脈為對象，觀察石英脈產狀與其他構造的關係，並由石英脈的結晶纖維判斷其主應變軸方向，最後結合石英脈中液包體所提供的溫壓資料，以其作為分析該地區地質構造之指標，以了解大禹嶺地區區域地質構造之變形過程。
大禹嶺地區的石英脈依產狀可分成雁型石英脈、平行板劈理型石英脈與截切板劈理型石英脈。由石英脈產狀與其他區域構造的觀察，以及石英脈中液包體的研究分析得知，雁型石英脈為大禹嶺複向斜雛形發育期，因變質砂岩單層中發生層間滑動所生成的，為該地區第一期生成之石英脈，而石英脈中所含之液包體資料顯示，液包體鹽度值約5wt%，均溶溫度約250-280℃，經推算校正得知該類石英脈於形成時的埋藏深度約7920公尺，形成溫壓分別約440-470℃/221.7Mpa；平行板劈理型石英脈為於複向斜已定形且板劈理形成之後，因岩體劇烈抬升造成孔隙水壓升高，使石英脈在此情況下於板劈理面處生成，為第二期石英脈，由石英脈中液包體的資料發現，液包體鹽度值約5wt%，均溶溫度約200-250℃，經推算校正得知該類石英脈於形成時的埋藏深度約5280公尺，形成溫壓分別約325-395℃/155.0Mpa；截切板劈理型石英脈則為岩體已被抬升至溫壓皆較低的淺處，因岩層仍受蓬萊運動作用影響而持續受力變形，導致此時的變形已由韌性變形轉變成如斷層、節理及石英脈等脆性變形，且該類石英脈呈板狀，位態與該地區節理相同，為最末期石英脈，而石英脈中液包體的資料發現，液包體鹽度值約3wt%，均溶溫度約170-200℃，經推算校正得知該類石英脈於形成時的埋藏深度約3960公尺，形成溫壓分別約265-295℃/121.6Mp。
在匡廬隧道以西之大禹嶺複向斜西翼，地層岩性以板岩為主，岩層平緩呈現正常序列，石英脈以第二期的平行板劈理型居多，且形態多為未受變形的板狀。匡廬隧道以東之大禹嶺複向斜東翼，地層岩性以變質砂岩夾板岩為主，岩層傾斜較陡呈現倒轉層序，石英脈則有第一期的雁型石英脈、第二期的平行板劈理型石英脈及第三期的截切板劈理型石英脈，其中平行板劈理型石英脈也有部分已受變形呈現褶皺彎曲形態或透鏡串腸形態。而複向斜東西兩翼石英脈產狀與類型的差異，可能與地層的岩性、岩層年代及層序是否倒轉有關。

關鍵字

石英脈 ； 液包體 ； 均溶溫度

並列摘要

When external forces compressed rocks, stress concentration usually occurred fractures. These fractures usually propagated in the minimum stress direction and developed crystal veins. Fluid inclusions are microscopic bubbles of liquid and gas that are trapped or healed fractures within a crystal, which preserves a record of the composition, temperature and pressure of the mineralizing environment. This study focused on the analyses of the quartz veins and fluid inclusions in the synclinorium of Tayuling Area, and tried to understand the geological events of this area.
According to the geometric shapes of Tayuling Area, the quartz veins can be classified into three groups, which separated all groups in the eastern side of the synclinorium and only second group in the western side: the first group of the quartz veins was aligned en echelon appearing in the metamorphic sandstone only, and it was developed by the bedding slip in the incipient stage of the folding. The result of the analysis in the first group shows that the density of the fluid inclusions is 5 wt% and the range of the homogenization temperature is 250-280℃; The second group of the quartz veins was parallel in the rock cleavage, and it was developed under the high pore pressure in the stage of the bedding rapid uplift. The result of the analysis in the second group shows that the density of the fluid inclusions is 5 wt% and the range of the homogenization temperature is 200-250℃; Finally, the third group of the quartz veins was almost perpendicular to the joints, and it was developed in the latest stage. The result of the analysis in the third group shows that the density of the fluid inclusions is 3 wt% and the range of the homogenization temperature is 170-200℃.The reasons making the differences between eastern and western part could be the lithologic units, the age and the overturning of the bedding.

並列關鍵字

quartz vein ； fluid inclusion ； homogenization temperature

參考文獻

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