地球化學(xué)及地質(zhì)意義
(1. 中南大學(xué) 有色金屬成礦預(yù)測(cè)教育部重點(diǎn)實(shí)驗(yàn)室，長沙 410083；
2. 中南大學(xué) 地球科學(xué)與信息物理學(xué)院，長沙 410083；3. 有色金屬華東地質(zhì)勘查局，南京 210007)
摘 要: 印度尼西亞塔里亞布島花崗巖位于東南亞陸緣殼體北緣。全巖Rb-Sr等時(shí)線測(cè)年結(jié)果表明，該花崗巖形成于中晚三疊世((227±2) Ma)，Isr=0.716 67±0.002 40，屬印支期的殼源S型花崗巖。巖石類型以二長花崗巖為主，富硅(w(SiO2)=75.92%~77.38%)、富堿(w(Na2O+K2O)＞7%)、富鉀(K2O/Na2O＞7)，貧鈣、鎂和鐵。稀土及微量元素方面富Rb、K、Th、U、Ta和Nb，貧Ba、Sr、P、Ti和Cr，具強(qiáng)烈的銪負(fù)異常(δ(Eu)=0.13~0.52)及鈰負(fù)異常(δ(Ce)=0.43~0.79)，反映出其經(jīng)歷過徹底的巖漿演化分異和斜長石分離結(jié)晶過程。結(jié)合區(qū)域地質(zhì)背景，晚三疊世前塔里亞布島位于新幾內(nèi)亞島北緣，尚未從岡瓦納大陸分離。塔里亞布島花崗巖形成于泛大洋洋殼對(duì)岡瓦納大陸陸殼北東部邊緣碰撞后的拉張−伸展環(huán)境，與該島鐵多金屬礦田同屬本次構(gòu)造−巖漿−成礦事件的產(chǎn)物。
關(guān)鍵字: 塔里亞布島；Rb-Sr年代學(xué)；地球化學(xué)；印支期；花崗巖
granite from Taliabu Island, Indonesia
（1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education,
Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
3. East China Mineral Exploration and Development Bureau, Nanjing 210007, China）
Abstract:The granite from Taliabu Island of Indonesia is situated in the north margin of Southeast Asia continental margin crustobody. The data of the whole rock Rb-Sr isotopic isochron show that the granite was formed in Middle to Late Trassic ((227±2) Ma), Isr=0.716 67±0.002 40. It belongs to Indo-Chinese epoch and S-type granite from crust source. The rock type is mainly monzogranite. Geochemically, the granite is rich in silica (w(SiO2)=75.92%−77.38%), alkali (w(Na2O+K2O)＞7%) and potassium (K2O/Na2O＞7), poor in calcium, magnesium and iron, and shows the enrichment of Rb, K, Th, U, Ta, Nb, and depletion of Ba, Sr, P, Ti and Cr, with an intensive negative Eu anomaly (δ(Eu)=0.13−0.52), and negative Ce anomaly (δ(Ce)=0.43−0.79). These geochemical characteristics indicate that the magma have gone through complete evolution and fractional crystallization of plagioclase. Combined with the regional geological setting, Taliabu Island is located in the north margin of New Guinea island which is not separated from Gondwana. The granite was formed in a post-collision extensional tectonic setting between the Panthalassa and the northeast margin of Gondwana. The granite is the same product with the Fe-polymetallic orefield in Taliabu island by the tectonism− magmatism−mineralization event.
Key words: Taliabu Island; Rb-Sr geochronology; geochemistry; Indo-Chinese epoch; granite
