塔北柯坪奥陶系碳酸盐岩地球化学特征及环境意义

GEOCHEMICAL CHARACTERS AND EWIRONMENTAL SIGNIFICANCE OF ORDOVICIAN CARBONATE ROCKS IN KEPING AREA,TARIM BASIN

塔里木盆地北部柯坪地区奥陶系可分为浅水台地和深水台盆两个相区以及５种不同类型的相带。化学分析表明该区地球化学特征与沉积环境有着极为密切的关系：（１）无论是常量元表，还是微量元表，在浅水台地相区其含量均较低，而在深水台益相区其含量明显增加。（２）随着水体加深，由局限台地相过渡到盆地相，Ｓｒ／Ｃａ×１０００比值由２．９逐渐增加到６．４。上述特征表明该区地球化学特征可作为相分析的标志之一。

Ordovician System in Keping area of Northern Tarim Basin is dominated by carbonate sediments and can be divided into platform and platform-basin factes zones and subdivided into five different factes types: restricted platform,open platform,platformmarginal shoal,neritic shelf and basin.Geochemical analyses indicates that geochemical characters are closely related tosedi-mentary environment in the study area:1.Different factes types have different geo-chemical characters,the contents of elements K,Na,Fe,Al and trace elements Sr,Ba,Mn,V,Niand B are low in the platform factes zone,but increase largely in the platformbasin factes zone, e. g., the everage content of K is less than 0.01% in the platform factes zone,and it is 0. 95% in the platform-basin factes zone.2.The everage Sr contentand Sr/Ca × 1000 ratio tend to increase gradually from restricted platform→open platform→platform marginal shoal→neritic shelf→basin, the ratio increases from 2. 9→3. 8→5. 3→6. 0→6. 4. The author agrees with J. Veizer at al that this is related to differentprimary carbonate minerals in different sedimentary environments.