本文選題：環(huán)斑花崗巖 + 鋯石SHRIMP��； 參考：《大地構(gòu)造與成礦學(xué)》2017年03期

【摘要】：以往將位于湘南、桂東北的都龐嶺花崗巖基分為西體、中體和東體三部分。野外觀察和巖相學(xué)研究表明,都龐嶺中體和東體主要由黑云母正長花崗巖、黑云母二長花崗巖和二云母二長花崗巖組成,巖石具斑狀結(jié)構(gòu),部分鉀長石斑晶呈橢球狀至球狀,具斜長石環(huán)邊,構(gòu)成環(huán)斑結(jié)構(gòu)。采用鋯石SHRIMP U-Pb法獲得都龐嶺中體和東體中環(huán)斑花崗巖的侵位年齡分別為226.6±6.9 Ma和209.7±3.1 Ma,均屬于晚三疊世,相當(dāng)于印支晚期。都龐嶺環(huán)斑花崗巖富硅、堿,貧鈦、磷、鎂和鈣,其Rb、Cs、Th、U、REE、Pb、Y含量和Rb/Sr、Rb/Ba比值較高,而Sr、Ba含量和Zr/Hf比值(8.16~25.01)較低,具強(qiáng)烈的Eu負(fù)異常(δEu=0.02~0.13),10000×Ga/Al比值(2.64~4.38,平均3.15)高,顯示A型花崗巖的地球化學(xué)特征。與華南印支早期S型花崗巖相比,都龐嶺環(huán)斑花崗巖的εNd(t)值(-8.0~-8.3)明顯偏高(前者低于-10),而tDM2值(1624~1645 Ma)則明顯偏低(前者1800 Ma),表明它們可能直接源于地殼物質(zhì)的部分熔融,但成巖過程中有地幔物質(zhì)的參與。都龐嶺環(huán)斑花崗巖的發(fā)現(xiàn)及其時代的確定,揭示了晚三疊世華南東部處于大陸裂解或造山后伸展的構(gòu)造環(huán)境。結(jié)合華南東部沉積/巖石大地構(gòu)造分析,認(rèn)為華南早中生代構(gòu)造體制的轉(zhuǎn)換發(fā)生在中、晚三疊世,而非前人所認(rèn)為的發(fā)生在中、晚侏羅世;同時,環(huán)斑花崗巖的出現(xiàn),指示了華南中生代大規(guī)模成礦作用的來臨,晚三疊世是華南中生代大規(guī)模成礦的第一個高峰期。
[Abstract]:In the past, the Dupangling granite base, located in the south of Hunan and northeast of Guangxi, was divided into three parts: the west body, the middle body and the east body. Field observations and petrographic studies show that the middle and eastern Dupangling bodies are mainly composed of biotite syenite granite, biotite monzogranite and bigite monzogranite, with porphyry structure, and some potash feldspar porphyry is ellipsoidal to spherical. With plagioclase ring edge to form a ring-spot structure. The emplacement ages of the central and eastern central granitic granites in DuPonling are 226.6 鹵6.9 Ma and 209.7 鹵3.1 Ma, respectively, obtained by zircon SHRIMP U-Pb method, which belong to the late Triassic and correspond to the late Indosinian period. DuPonling ringlike granites are rich in silicon, alkali, titanium, phosphorus, magnesium and calcium. Their RB ~ (+) C ~ (+) C ~ (1) ~ (+) ~ (10 ~ (10) ~ (10 ~ (10) 脳 Ga/Al) = 2.644.38, with an average of 3.15), and the content of RbC ~ (2 +) and the ratio of RB / Sr ~ (+) ~ (B / Ba) are high, while the ratio of Sr ~ (+) Ba and Zr/Hf is 8.16 ~ 25.01). It has a strong negative EU anomaly (未 -EU _ (0.02N) 0.13 ~ (10 000) ~ (10) 脳 Ga/Al = 2.644.38, average 3.15), which shows the geochemical characteristics of A-type granites. Compared with the early Indosinian S-type granites in South China, the Dupangling ring-macular granite has a significantly higher 蔚 -NdT value (-8.0 ~ 8.3) (the former is lower than -10 ~ (-1), while the tDM2 value of 1624 ~ 1645 Ma) is obviously lower (the former is 1800 Ma ~ (-1), indicating that they may have originated directly from partial melting of crustal material. But the mantle material is involved in the diagenetic process. The discovery and dating of the DuPonling ringed granite reveal the tectonic environment in which the eastern part of South China is located in the continental cleavage or post-orogenic extension in the late Triassic. Based on the analysis of sedimentary / lithotectonics in eastern South China, it is concluded that the transformation of early Mesozoic tectonic systems in South China occurred in the Middle and late Triassic, rather than in the Middle and late Jurassic, and that the occurrence of macular granites occurred in the early Mesozoic in South China. The late Triassic is the first peak of Mesozoic large-scale mineralization in South China.
【作者單位】： 武漢地質(zhì)礦產(chǎn)研究所;中國地質(zhì)調(diào)查局花崗巖成巖成礦地質(zhì)研究中心;
【基金】：中國地質(zhì)調(diào)查局地質(zhì)礦產(chǎn)調(diào)查評價項目(1212010813061、1212011085405)資助
【分類號】：P588.121

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