編號： 026

題　名：台灣西部沿海海砂調查

The Investigation of Sea Sand along the Western Taiwan Offshore Area.

研究者：陳汝勤 ; 林斐然 ; 姚永昌 ; 林再興 ; 陳時祖 ; 高瑞棋 ; 艾克非

Chen,Ju-Chin ; Lin,Fei-Jan ; Yao,Yung-Chang ; Lin,Tsai-Hsing ; Chen,Shih-Tsu ; Kao,Ruey-Chy ; Ai,Koe-Fe

機構名稱：經濟部中央地質調查所 (CGSG)

研究日期： 1991/07 - 1992/06

出版日期： 1992/06

頁冊數： 85

中文摘要： 81年度本計畫調查台灣中西部沿海水深20公尺以上之地區海砂分布及儲藏的情形,北起通霄外海,南至北回歸線,包括澎湖群島。調查項目有海砂顆粒分析、化性分析、重錘貫入取樣、海底地形調查、海砂儲藏量估計等。研究結果除重錘貫入取樣及海底地形調查受到天候影響進度落後外,餘則均已完成。台灣中西部沿海海砂之粒度一般是介於0.phi.-4.phi.之間,不過多半是以1至2.phi.的中砂為主,澎湖沿海海砂粒度介於0.5.phi.-3.5.phi.之間,平均為2.phi.之中砂,而海峽陸棚砂則為細砂和極細砂(2.phi..sim.>4.phi.)。中西部沿海海砂標準偏差值介於0.23.phi.-0.90.phi.間,屬極良淘選至中淘選度平均為次良淘選。澎湖地區海砂淘選度較差,其標準偏差值約為1.8.phi.,至於陸棚砂中,其準偏差值變化大,自良淘選至劣淘選皆有,而為劣淘選。本區海砂之礦物組成以石英、長石為主,亦含少量之伊利石、高嶺土和綠泥石,而方解石、霰石則出現於王功以南至雲林台西沿海的ST92-ST116之標本中,澎湖沿海之海砂則主要為方解石、霰石,至於陸棚砂則以石英、長石、方解石、霰石為主,比較缺乏黏土礦物如綠泥石高嶺土、伊利石等。本區海砂及陸棚砂之化學特性為含SiO/sub 2/高時(約 60%-90%),Na/sub 2/O、K/sub 2/O、 Al/sub 2/O/sub 3/、MgO均與SiO/sub 2/呈反比關係,而 CaO及L.O.I.則維持一固定值;反之在SiO/sub 2/60%時 Na/sub 2/O、K/ sub 2/O、Al/sub 2/O/sub 3/與SiO/sub 2/呈 正變關係CaO、 MgO與SiO/sub 2/呈負變關係。根據海砂礦物組成研判台灣中西部原層沈積岩層及中央山脈東側古生代變質岩可能是中西部海砂及部分陸棚砂之來源。澎湖沿海海砂中含有豐富之生物殘骸,島的四週常有礫石出現及島之本身不大,顯示其提供砂之可能性很小,其海砂係由源自台灣島之現代沈積物及殘餘沈積物混合而成,而海峽陸棚上的殘存沈積物可能來自中國大陸。依據鑽探資料及顆粒分析結果初步評估台灣中西部沿海海砂之礦量約為3.3*10/sup 10/-16.6*10/sup 10/噸。

英文摘要： In 1992, under this program, we have investigated the sea sand speard and storage condition, from offshore of Tunghsiao in the north to the Tropic of Cancer in the south, at the place where the sea water depth over 20m which is along the middle part of Taiwan coast area, include Penghu Islands. This research include sea sand grain analysis, chemical analysis, heavy-weight penetration sampling, sea bed morphology survey, sea sand storage estimation,... etc. Because of the weather condition, the heavy-weight penetration sampling and sea bed morphology survey are still not accomplished; as to the grain size analysis of sea sand about this area is generally amid 0 and 4.phi., but mostly is 1 to 2.phi. medium sand; the sand of Penghu Island is amid 0.5.phi. and 3.5.phi., its average is 2.phi. medium sand; and the sand on the shelf is fine to very fine sand (2->4.phi.). The standard deviation value of middle west offshore sea sand is between 0.23-0.90.phi., which belongs to very good to fine sorting, the average is good sorting. Sea sand sorting in Penghu Islands area are poor, its standard deviation value varied much, from good to bad sorting, so it is bad sorting. The mineral constituents of this area mainly is quartz and feldspar, and also contain small amount of illite, kaolinite and chlorite, the calcite and aragonite occur in the ST-92 to ST116 samples only, which is located at the area from south of Wangkong to Taihsi of Yunlin. Penghu Islands 's sea sand mainly composed of calcite & aragonite, as to the shelf's sand which is mainly quartz, feldspar, calcite, aragonite but lack of clay minerals like chlorite, kaolinite, illite etc. The chemical characteristics of this area's sand and shelf's sand is about when SiO/sub 2/ content is high (about 60-90%), Na/sub 2/O, K/sub 2/O, Al/sub 2/O/sub 3/, MgO all are in inverse relation with the SiO/sub 2/, and CaO and L.O.I maintain its fixed value; but when SiO/sub 2/ value is less than 60%, Na/sub 2/O, K/sub 2/O, Al/sub 2/O/sub 3/ show proportional relationship with SiO/ sub 2/; CaO, MgO show contrary relation to SiO/sub 2/. According to the sea sand mineral constituents, the thick sedimentary formations of Taiwan middle west and the paleozoic metamorphic rocks of the east side of Central Range are possibly the sources of the sea sand of this area and some part of the shelf's sand. The Penghu Islands's sea sand contain abundant of relics of bios; since the island surroundings can often find the gravels and because the islands are not large, so this reveals that its possibility to give the sand is very small, its sand are mixture of Taiwan main island's modern deposits and the local Penghu island's residual sediments, and the residual sediments on Taiwan shelf may come from the Mainland China. In reference the drilling core information and the result of grain analysis, we can approximately to estimate the sea sand resources storage of Taiwan middle west part of offshore area is about 3.3*10/sup 10/-16.6*10/sup 10/ tons.