2010-01-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/671797摘要：台灣西南海域同時擁有活動大陸邊緣與被動大陸邊緣兩種不同的大地構造系統，皆是天然氣水合物形成之良好環境。過去研究顯示西南海域氣體特徵有極大的區域性變化。西南海域大地構造可能對於地層中甲烷移棲之區域性差異及其對淺層與深部沉積物地質地化特徵有極大的影響，然而對於整個海脊構造及不同海脊構造之間甲烷移棲及沉積物地質地化特徵的區域性差異尚未能有全盤的瞭解。因此「地球化學調查」計畫擬分年針對不同之海脊構造進行全面性的岩心採樣及TowCam調查研究，深入探討從增積岩體前段至後段，以及被動大陸邊緣海域，不同海脊構造環境之甲烷移棲現象及其對於淺層沉積物地質地化特徵的影響，以瞭解調查區域內何處呈現甲烷氣從深部強烈往上移棲的現象，進而判定該強烈甲烷移棲的區域地層中可能賦存豐富的天然氣水合物，並進一步探討何種大地構造環境為天然氣水合物最佳的賦存區域。 99年度計畫各項研究工作分由六個子計畫進行： 子計畫(I)：台灣西南海域海水與沉積物之氣體化學組成—楊燦堯教授 子計畫(II)：台灣西南海域地質微生物(細菌與太古生物)多樣性調查與天然氣水合物形成與分解機制探討—賴美津教授 子計畫(III)：台灣西南海域自生性碳酸岩及硫物種之變化與天然氣水合物賦存之關係 —林曉武教授 子計畫(IV)：台灣西南海域天然氣水合物探勘熱區之黏土與自生礦物研究—江威德教授 子計畫(V)：台灣西南海域沉積物之古地磁定年及磁學性質研究—洪崇勝教授 子計畫(VI)：台灣西南海域沉積物基本性質與天然氣水合物賦存之關係—陳汝勤教授 本計畫擬探討天然氣水合物，其氣體在沉積物內之擴散與噴發及受微生物產生之生地化變化，與註記於自生碳酸岩與硫化礦物等之特徵，並探討其沉積年代與噴發擴散時間，來瞭解天然氣水合物在台灣西南海域活動大陸邊緣增積岩體之前、中、後段與被動大陸邊緣二環境之形成與積蓄，並藉著沉積物之基本性質來評估天然氣水合物之經濟價值。 99年度計畫調查工作擬分成兩大項目，包括(1) MD超長岩心採樣調查、(2)增積岩體後段區之枋寮海脊與古高屏峽谷深水扇區之6~18米活塞岩心採樣與TowCam海床地貌拍攝調查。 本計畫預計於2010年5月份利用法國研究船Marion Dufresne號進行16~24個站位之30~50米超長岩心樣品採集，以期(1)直接採集到深部沉積物中的天然氣水合物；(2)瞭解台灣西南海域深部沉積物與淺層沉積物之甲烷移棲與地質地化特徵的異同；(3)瞭解不同區域之深部沉積物與孔隙水地質地化特徵的空間與時序性變化，及其與甲烷移棲和天然氣水合物賦存之關係；(4)瞭解地質微生物種類隨岩心深度的變化及其與甲烷移棲之關係；(5)建構具有碳十四定年之磁場世紀變化曲線，以助於天然氣水合物相關地質事件之年代對比；(6)瞭解台灣西南海域沉積歷史，建立長時間尺度之甲烷移棲模式。 本計畫亦預計將申請海研一號7天航次，以期能完成執行枋寮海脊及古高屏峽谷深水扇區之海床地貌TowCam拍攝、USBL水下定位及6~18米活塞岩心採樣，以期(1)瞭解沉積物與孔隙水地質地化特性之空間與垂直分佈變化，及其與甲烷滲漏、移棲和天然氣水合物賦存之關係；(2)瞭解不同大地構造與地層結構之差異對於沉積物地質地化特性的影響及其與甲烷移棲之關係；(3)瞭解海床地貌特徵分佈變化及其與甲烷移棲之關係；(4)瞭解地質微生物種類之區域性差異及其與甲烷移棲之關係；(5)提供預定鑽探井位與其周圍沉積物之地質地化資料。 本計畫亦擬與國外研究單位進行合作，希望能藉助國外先進單位之研究船隻與設備（如ROV、MeBo、Lander等)，探討表層與深層之天然氣水合物存在環境與控制因素，期能於未來四年期計畫界滿內評估台灣西南海域之天然氣水合物之儲量、生地化變化與建立未來鑽探之基礎資料。 <br> Abstract: The existence of both passive and active margin adjacent to each other offshore SW Taiwan is very unique in the marine environment, especially in evaluating formation of gas hydrate under different tectonic settings. South China Sea adjacent to Taiwan provides such a rare opportunity in studying and comparing gas hydrate formation, migration and sea floor phenomena at both active and passive margin environments. Extensive samplings during the past four years in the Taiwan gas hydrate research program facilitate our basic understandings toward gas hydrate formation and subsequent bio-geochemical processes. Typical phenomena, e.g. gas plume, chemosynthetic community, anomaly pyrite and authigenic carbonate formation, chimney and chemoherm buildup, demonstrate that abundant gas hydrate exist under the sea floor in the South China Sea adjacent to Taiwan. However, little is known about how and when gas migration occurs and nature of subsequent microbial activities and other geochemical processes that may alter the gas hydrate formation and migration in both active and passive margin in these areas. Furthermore, findings of hydrothermal like of chemo-communities in the cold seep environment further raise the question of how gas and fluid migration and subsequent chemical processes that may generate such an unusual chemosynthetic community. In order to understand gas hydrate formation in these two environments and to understand the cause and effect of gas hydrate migration, we have re-grouped related PIs in the field. We intend to study gas composition, microbial process and subsequent pore water variations, authigenic minerals formation, sedimentation and stratigraphy and timing of carbonate formation, and sediment properties. Our group includes: (I) T. F. Yang: Studies on the gas compositions in sea water and sediments offshore southwestern Taiwan. (II) M.-C. Lai: Geomicrobial diversity in the gas hydrate potentials regions offshore southwestern Taiwan and its role in gas hydrate formation and degradation (III) S. Lin: Authigenic carbonate formation and sulfur cycle in the active and passive margin offshore southwestern Taiwan. (IV) W.-T. Jiang: Clay- and authigenic-mineral studies of the favorable sites for gas hydrate exploration offshore southwestern Taiwan (V) C.-S. Horng: Paleomagnetic dating and magnetic properties of sediments offshore southwestern Taiwan (VI) J.-C. Chen: The relationship between sediment properties and the occurrence of gas hydrate offshore southwestern Taiwan The 2010 works include MD giant piston core sampling, TowCam survey and 6~18m piston core sampling in the Fangliao Ridge and Kaoping Canyon paleo-fan region. About 16-24 sites giant piston cores will be collected during MD cruise on May, 2010. The goal of MD cruise includes (1) to collect gas hydrate solidified samples; (2) to understand spatial and temporal variation of methane migration and subsequent geochemical processes in deep sediments; (3) to understand differences of those geochemical processes in shallow and deep sediments; (4) to understand spatial and vertical variation of microbial diversity and the relationship with methane migration; (5) to construct a reliable and continuous geomagnetic secular variation curve with carbon-14 ages on the sedimentary sequences of the background sites; (6) to understand sedimentary history offshore SW Taiwan in order to establish a long-term methane migration model. We will apply an 7-days ORI cruise to carry out TowCam survey and piston core sampling of the Fangliao Ridge and Kaoping Canyon paleo-fan region. The goal of ORI cruise includes (1) to understand spatial variation of geochemical characteristion and relationship with methane migration and gas hydrate; (2) to understand the influence of tectonic structures on the spatial variations; (3) to understand spatial variation of methane-related seafloor features; (4) to understand spatial variation of microbial diversity; (5) to provide geochemical data for future drilling site selection.天然氣水合物活動大陸邊緣被動大陸邊緣冷泉甲烷微生物硫酸鹽還原化學自營性生物自生性碳酸岩黃鐵礦古地磁定年孔隙率流體移棲gas hydrateactive marginpassive margincold seepmethanemicrobialsulfate reductionchemosynthetic communityauthigenic carbonatepyritepaleomagnetic datingporosityfluid migration