The Late Precambrian Paleo-Ocean Evolution of the Southeast Yangtze Continental Margin: REE Record
-
摘要: 本文采用中子活化方法分析了晚震旦~早寒武纪19件样品的稀土元素组成,发现硅质岩石REE配分形式有着复杂的变化,初步可以划分为五种类型,包括“台地型”、“红海型”、“海水型”及两种特殊的配分形式。剖面上Ce异常由小到大的演变反映了古海洋底层水由缺氧环境向氧化条件的逐渐转化。正Eu异常的出现代表了热水沉积事件的存在。Abstract: We report REE (rare earth elements) data of 19 samples from Upper Sinian - Lower Cambrian chens by neutron activation analysis. The REE patterns with respect to an average shale show complicate changes and are preliminarily classified into different types, including "platform-type", "Red Sea-type", "seawater-type"and two distinctive types. The Ce depletion in the section exhibits a progressive increase from the lower to upper beds. The Ce anomaly,as an indicator of redox conditions, reveals that paleo-ocean bottom seawater in this area was anoxic during Late Precambrian and an oxidizing environment occurred in Early Cambrian.The occurrence of positive Eu anomaly may indicate submarine hydrothermal deposition.
-
Key words:
- Chert /
- REE /
- Paleo-ocean /
- Anoxic environment /
- Submarine hydrothermal event
-
[1] 1.夏文杰等,1993,湘西地区震旦纪菌藻硅质岩特征及形成机理探讨;矿物岩石,13(3):21-28。
2.伊海生,1994,扬子地台东南大陆边缘上震旦统硅质岩的超微组构及其成因;地质学报,68(2):132-141。
3.Shimizu, H. et al.,Cerium in chert as an indication of marine environment of its formation. Nature, 266(1977):346-348.
4.Steinberg, M. et al.,In: Iijim A. Hein,J. R.,Siever, R. ed: Siliceous deposits in the Pacific Region. Amsterdam.Elsevier, 193-210.
5.Murray, R. W. et al.,Rare earth elements as indicators of different marine depositional environments in cherts and shale. Geology, 18(1990):268-271.
6.Wang, Y. L. et al.,Rare earth element geochemistry of south Atlantic deep sea sediments: Ce anoaly change at-4Mv. Geochim. Cosmochim. Acta, 50(1986),1337-1355.
7.赵振华等,1989,大阳岔寒武-奥陶系界线层剖面的无纹钢及沉积岩微量元素地球化学,中国科学B辑,8:877-887。
8.吴明清等,1992,塔里木盆地西缘古海洋氧化还原条件的变化-介壳化石的稀土元素钵异常证据;中国科学B辑,2:206--215。
9.沉积地球化学编写组,1989,沉积作用过程中稀土元素的地球化学;岩相古地理,39(1):58-v66. 40(2):44-51。
10.Piper, D. Z.,Rare earth elements in the sedimentary cycle: a summary. Chem. Geol. 14(1974):285-304.
11.Haskin, M. A. et al.,Rare earth in sediments. J. Geophy. Res.,71(1966):6091-6105.
12.Nance, w. b. et al.,,Rare earth element patterns and crustal evolution-Archean sedimentary rocks from Kalgoorlie,Australia. Geochim. Cosmochim. Acta, 41(1977):225-231.
13.Goldberg, e. D. et al.,Rare-Earth distributions in the Marine environment. J. Geophys. Res. 68(1963):4209-4217.
14.Elderfield, H. et al.,The rare earth elements in seawater. Natue, 296(1982):214-219.
15.Klinkhammer, G. et al.,Rare earth elements in seawater near hydrothermal vents, Nature, 305(1983):185-188.
16.Addy, S. K.,Rare earth element patterns of manganese nodules and micronodules from northwest Atlantic. Ueochim.Cosmochim. Acta.,43(1979):1105-1118.
17.Marchig, V. et al.,Sediments from a hydrothermal field in the central valley of the CUalapagos Rift spreading center.Marine Geol.,76(1987):243-251.
18.Michard,A. et al. Rare earth elements and uranium in high-temperature solutions from East Pacific Rise hydrother-malvent field (13 N). Nature, 303(1983):795-797.
19. Fryer, B. J.,Rare earth evidence in iron-formations for changing Precambrian oxidation states. Geochim. Cos-mochim. Acta, 41(1977):361-367.
20.Graf, Jr.,Rare earth elements, iron formations and sea water. Geochim. Cosmochim. Acta, 42(1978):1845-1850.
21.Courtois, C. et al.,Distribution des terres rarer et de queiques elemennts en trace dins les sediments recents des foss-es de la Mer Rouge. Chemical Geology, 20(1977):57-72.
22.Fleet,A. J.,In:P. A. Rona(Editor),Hydrothermal processes at seafloor spreading centers. plenum. New York, N.Y.,1983. 539-555.
计量
- 文章访问数: 607
- HTML全文浏览量: 19
- PDF下载量: 407
- 被引次数: 0