野柳砂岩風化特性之研究

Abstract

本研究針對野柳景觀區內不同岩性的礦物組成、岩象特徵以及化學成分作分析，以瞭解地形發育與岩石特性間的關係。 研究結果發現，在礦物組成上，石英、長石與高嶺土為主要的組成礦物。蕈岩頭部與薑石二種岩石的方解石和石英含量，比蕈岩頸部和風化窗多。由蕈岩頭部與薑石岩石薄片的觀察，其岩象顯示方解石充填於礦物顆粒之間的現象；而蕈岩頸部和風化窗的岩象，不透明礦物分佈多，且於礦物顆粒間充填的情形十分明顯。在化學成分方面，蕈岩頸部和風化窗的水溶性鹽類離子濃度含量明顯高於蕈岩頭部與薑石，鈉離子在蕈岩頸部中的最高值可達1280 mg/kg，氯離子則達13040 mg/kg；此現象不但說明風化窗與蕈岩頸部受鹽的破壞程度高，並顯示鹽風化(salt-weathering)可能是野柳區域內主要的風化營力。風化窗的離子濃度在不同岩石深度的變化是由表面往內部遞減，蕈岩頸部則是往內部遞增。風化窗的鈣和硫酸根離子的最高值分佈於表面，達500、474 mg/kg。

This study focuses on the mineral compositions, chemical properties and petrography features in different petrology of yehliu, Taiwan northern in order to realize the characteristics of weathering. Quartz, feldspar and kaolinite are the main minerals in all types of rocks of Yehliu. There are more quartz and calcite in ginger rock and head of mushroom rock. This situation maybe the reason that it is much stronger in strength. For the petrographic features, there are more calcite filled in the pores than at head of mushroom rock. The neck of mushroom rock has many matrixes and some of them intrude into mineral grains. The concentrations of water soluble ions in tafoni and neck of mushroom rock are much higher then ginger rock and head of mushroom rock. The difference between the concentration of the sodium and chlorine even goes few tens-fold. It implies that salt is the main element within coastal weathering process. During weathering processes, there are some ion diffusion and deposition in rocks. The distribution of ion concentrations is relatively lower at neck of mushroom and tafoni. There are more calcium and sulfur deposit on the surface of tafoni. It can produce II more gypsum and make sandstone much stronger and reduce the weathering processes into the inner part.