菲律賓明多洛島之岩石地球化學與定年分析結果及其在地質構造演化上之隱示

Geochemical data and dating results from Mindoro, Philippines and their tectonic implications

陳皇伶(Huang-Lin Chen)

指導教授 ： 楊燦堯

國立臺灣大學/理學院/地質科學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.01224

摘要

明多洛島位於巴拉望陸塊（Palawan Continental Terrane）和菲律賓活動帶 （Philippine Mobile Belt）兩個陸塊之間。本研究在兩板塊交界的縫合帶及其附近採樣，進行地球化學以及定年分析，包括：核飛跡定年、氬氬定年及鈾鉛定年，以進一步探討明多洛島上之縫合帶特性。縫合帶上蛇綠岩套樣本之化學分析結果顯示，一些樣本具有中洋脊玄武岩之特色；由其稀土元素含量，又可區分成LREE富集的E-MORB、以及LREE虧損的N-MORB的樣本；其中在明多洛島西北角的火成岩樣本，呈現洋島玄武岩（OIB）之地球化學特徵。另外，本島變質岩區之火成岩樣本、變質岩樣本以及沉積岩樣本，則具有島弧岩漿特性之高場力鍵結元素虧損的現象。
由明多洛島西北部變質岩區的變質火成岩鈾鉛定年與低度變質的閃長岩氬氬定年分析結果，指示了本地區兩個岩漿活動時期：250 Ma左右與中國南方海南島有關的島弧岩漿活動；以及83 Ma左右區域性的岩漿活動，而流域中河砂之鋯石鈾鉛定年結果也顯示了這兩個年代之來源。角閃岩中角閃石之氬氬定年分析結果，則指示了一個在29 Ma左右的熱變質作用年代，可能為一次碰撞事件；磷灰石核飛跡定年則顯示了在5 Ma至0.6Ma間，巴拉望陸塊與菲律賓活動帶的碰撞抬升所造成的剝蝕作用年代。

關鍵字

地球化學 ； 鈾鉛定年 ； 核飛跡定年 ； 氬氬定年 ； 明多洛島

並列摘要

The Mindoro is located between Palawan Continental Terrane and Philippine Mobile Belt. We collected the samples near the suture zones and conducted geochemical analysis and dating for these samples to discuss the affinity of suture zone. The basalts from the ophiolite belt show two different affinities. Some samples show the signature of E-MORB with LREE enrichment; meanwhile, the other sample exhibits N-MORB signature with LREE depletion. On the other hand, samples from NW part of the island show the OIB signature. The volcanic rocks, metamorphic rocks and sedimentary rocks from Mindoro metamorphics show characteristics of HFSE depletion, which infer those samples were products of island arc.
The volcanic samples from northwest Mindoro show that there were two major volcanic events in this area. First event was 250 Ma of U-Pb dating and hornblende Ar-Ar dating for granodiorite and diorite, respectively. This volcanic event can correlate with Permian magmatism occurred in South China. The U-Pb dating of rhyolite sample shows the thermal event record of 83 Ma, which may represent a local volcanic event. A date of 29 Ma was obtained from the amphibolite samples by hornblende Ar-Ar dating technique. It infers that a collision event occurred during this period. Fission track data show the exhumation age of Palawan Continental Terrane and Philippine Mobile belt from 5 Ma until 0.6 Ma.

並列關鍵字

geochemistry ； U-Pb dating, fission track dating ； Ar-Ar dating ； Mindoro

參考文獻

鍾靈 (2006) 西藏東部嘉黎斷裂帶熱歷史之核飛跡定年證據及其大地構造之隱示。國立台灣大學地質科學研究所碩士論文，共71頁。

朱秋紅 (2005) 龜山島高美安山岩之岩漿成因。國立台灣大學地質科學研究所碩士論文，共99頁。

Boynton, W., 1984, Geochemistry of the rare earth elements: meteorite studies: Rare earth element geochemistry, p. 63-114.

Brandon, M.T., 1992, Decomposition of fission-track grain-age distributions: American Journal of Science, v. 292, p. 535-535.

Brandon, M.T., 1996, Probability density plot for fission-track grain-age samples: Radiation Measurements, v. 26, p. 663-676.