【摘要】：塔里木盆地玉北地區(qū)蓬萊壩組發(fā)育粉-細(xì)晶自形白云巖、中晶自形-半自形白云巖、粗晶自形-他形白云巖三種白云巖類型。粉-細(xì)晶白云巖具紋層狀構(gòu)造,稀土元素配分模式、總稀土含量與同期灰?guī)r相似,氧同位素組成與同期海水成因的白云巖相近,表明白云巖化流體為同期海水,較高的鹽度指數(shù)指示了相對濃縮的海水條件,較低的有序度值反應(yīng)出快速的白云巖化過程,為準(zhǔn)同生白云巖化的產(chǎn)物,白云石晶間均勻充填富Fe、富Si及高~(87)Sr/~(86)Sr比值的陸源物質(zhì),表明玉北地區(qū)在蓬萊壩組粉-細(xì)晶白云巖沉積期由于相對海平面較低從而受到陸源物質(zhì)混入的影響。中晶白云巖和粗晶白云巖的稀土元素配分模式、總稀土含量、~(87)Sr/~(86)Sr比值等與同期海水特征相似,表明白云巖化流體為海水,可見殘余顆粒結(jié)構(gòu),成巖溫度較低,埋藏較淺,為埋藏的海水以及沿原始顆�；�?guī)r的粒間孔及可能存在的裂縫等通道向下運(yùn)移的海水提供的Mg~(2+)導(dǎo)致的白云巖化,后期重結(jié)晶作用破壞了粗晶白云巖中的殘余顆粒結(jié)構(gòu)并導(dǎo)致其Fe、Mn含量及成巖溫度、有序度值高于中晶白云巖,Sr含量及δ~(18)O值低于中晶白云巖。部分中-粗晶白云石邊緣可見加大邊,表明后期存在少量他源流體導(dǎo)致的次生加大作用。
[Abstract]:There are three types of dolomite in Penglai formation of Yubai formation in Tarim Basin: silt-fine-crystalline automorphic dolomite, mesomorphic and semi-automorphic dolomite, coarse allogeneic dolomite. The silt-fine-grained dolomite has a lamellar structure, a REE distribution model, a total rare earth content similar to that of the corresponding limestone, and an oxygen isotope composition similar to the dolomite formed in the same period, which indicates that the dolomitization fluid is the contemporaneous seawater. The higher salinity index indicates the relatively concentrated sea water condition, the lower order value reflects the rapid dolomization process and the product of quasi-syngenic dolomitization, and the dolomite intergranular is evenly filled with Fe, rich Si and high ~ (87) Sr/~ _ (86) Sr. The results show that the silt-fine dolomite of Penglai formation in Yubei area was influenced by the mixing of land-based materials due to the relatively low sea level during the sedimentary period of the silt-fine-grained dolomite. The REE distribution model of mesocrystalline dolomite and coarse dolomite and the ratio of total rare earth content of ~ (87) Sr/~ (86) Sr are similar to those of seawater in the same period, indicating that the dolomitization fluid is seawater with residual grain structure, low diagenetic temperature and shallow burial, and the distribution pattern of REE in mesocrystalline dolomite and coarse-grained dolomite is similar to that in seawater. The dolomization caused by Mg~ (2) for buried seawater and seawater that moves downward along channels such as intergranular pores and possible fractures of the original granular limestone, Later recrystallization destroyed the residual grain structure of coarse dolomite and resulted in its Fe,Mn content and diagenetic temperature. The order value was higher than that in mesocrystalline dolomite Sr content and 未 ~ (18) O value lower than that in mesocrystalline dolomite. The edge of some meso-coarse dolomite is enlarged, which indicates that there is secondary augmentation caused by a small amount of other fluids in the later stage.
【作者單位】： 北京大學(xué)地球與空間科學(xué)學(xué)院;北京大學(xué)石油與天然氣研究中心;
【基金】：中國石油化工股份有限公司科技開發(fā)部項目(P14128、P16112) 中國地質(zhì)調(diào)查局項目(DD20160175-1-1) 國家自然科學(xué)基金項目(41572117)聯(lián)合資助
【分類號】：P618.13

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