中文摘要：

重庆石柱上二叠统吴家坪组硅质岩广泛发育。通过野外剖面的观察和硅质岩主量、稀土及同位素的分析,认为吴家坪组硅质岩为受到热水影响的生物成因。其化学成份以SiO2为主,质量分数为65.52%~97.76%,富集Fe,Mn等元素,Al/（Al＋Fe＋Mn）平均值为0.38,但约一半样品的Al/（Al＋Fe＋Mn）比值接近于纯生物成因的比值;REE总量平均值为38.55×10-6,δCe值为0.48~0.93,为中-弱负异常,δEu值为0.70~1.12,无明显的正负异常;δ30Si的值为0.7‰~1.4‰,更多地接近（或高于）现代放射虫的δ30Si;根据δ18O计算出硅质岩形成时古海水的温度为45℃~95℃。硅质岩的形成与火山活动和断裂有关,下渗的海水与岩浆热液混合,并被加温,溶解了大量SiO2等;然后以热泉形式通过断裂喷出,使附近海水中SiO2含量极大提高,促使放射虫和海绵等硅质生物大量繁殖,最终形成生物硅质岩沉淀下来。

英文摘要：

Silicalites are widely distributed in the Wujiaping Formation of Upper Permian in the Shizhu area,Chongqing.Through detailed field observation,combined with the data of macro-analysis,REE and isotope of silicalites,it is indicated that the silicalites of the Wujiaping Formation are characteristic of biogenesis with hydrothermal activity.The contents of SiO2 are relatively high with the value of 65.52%~97.76%.The ratio of Al/（Al＋Fe＋Mn） is regarded as a helpful criterion for identifying hydrothermal silicalites from other origin silicalites.The average ratio of Al/（Al＋Fe＋Mn） obtained in the Wujiaping Formation is 0.38.However,about half of the samples are close to the ratio of pure biogenic.The REE contents of silicalites are low（38.55×10-6）,with mid enrichment of HREE and weak negative anomaly of Ce,with the value of 0.48~0.93.Eu has a value of 0.70~1.12,showing no evident anomaly.The Silicon（δ30Si） is of a value 0.7‰ ~ 1.4‰,similar to（or above） modern radiolaria δ30Si.Based on the Oxygen isotope（δ18O） fractionation equation of chert and water,the paleo-temperatures of the silicalites in the Wujiaping Formation is 45 ℃~95 ℃.There were many syn-depositional faults and volcanism in the late Permian in eastern Sichuan basin.And the heat source responsible for hydrothermal convection is presented in study area.Present studied section is just located near the Qiyaoshan fault,which could be the pass of hot liquid from deep crust.At that time,sea water encountered and was heated with magmatic liquid,and then dissolved much SiO2 and other elements.The warmer sea water with dissolved SiO2 sprayed out from the faults,which made sea water near the fault contain much more SiO2 and enable radiolarians and siliceous sponges large reproduction.Finally,sea water enriched in SiO2 grew much better and siliceous biology died and set down to form bio-siliceous rock.