CAJ | 학술논문

塔里木盆地寒武系发育层状硅质岩和硅化岩,层状硅质岩主要发育于塔东下寒武统深水沉积相区;硅化岩发育于塔东上寒武统斜坡沉积区与西部台地区寒武系白云岩中.根据显微结构特征,可将硅化岩分为放射状硅化岩与交代残余结构硅化岩两种.分析结果表明,层状硅质岩在Al-Fe-Mn三元图中位于正常海水沉积硅质岩区内,在微量元素平均地壳标准化图解上显示平缓右倾的特征;层状硅质岩Si同位素组成δ~(30)Si为0.9‰～1.4‰,O同位素组成δ~(18)O为21.4‰～24.4‰,与沉积型硅质岩相吻合,指示了正常海水沉积成因.硅化岩区别于层状硅质岩的典型特征是具有高U异常的特征;罗西斜坡放射状硅化岩具有较高的微量元素和稀土元素含量(∑REE为18.8～96.9μg/g)与较低的Si、O同位索值(δ~(18)O和δ~(30)Si值分别为15.8‰和1.7‰);西部台地区交代残余结构硅化岩具有较低微量元素和稀土元素含量(∑REE为0.58～2.61μg/g)与较高的830Si(1.0‰～3.8‰)、δ~(18)O(21.6‰～27.0‰)值特征.盆地东西部硅化岩的地球化学差异可能与硅化流体的温度差异有关,罗西斜坡放射状硅化岩硅化温度相对更高;另一方面,硅化过程对H_4~(30)SiO_4选择性较高,因而形成的交代石英具有较高的δ~(30)si值.根据古城4井硅化岩包裹体均一温度与交代石英的O同位素值计算得到交代流体的δ~(18)O值为9.1‰.该值与酸性岩浆水的δ~(30)O值相似,指示了硅化流体可能来自于岩浆或变质水;以δ~(18)O值(9.1‰)作为西部台地区硅化流体的O同位素值,计算得到西部台地区硅化岩硅化流体温度为101.3～158.5℃.根据石英O同位素温度计计算的硅化流体温度呈东高西低的趋势,指示了硅化流体可能来自台地东部.
탑리목분지한무계발육층상규질암화규화암,층상규질암주요발육우탑동하한무통심수침적상구;규화암발육우탑동상한무통사파침적구여서부태지구한무계백운암중.근거현미결구특정,가장규화암분위방사상규화암여교대잔여결구규화암량충.분석결과표명,층상규질암재Al-Fe-Mn삼원도중위우정상해수침적규질암구내,재미량원소평균지각표준화도해상현시평완우경적특정;층상규질암Si동위소조성δ~(30)Si위0.9‰～1.4‰,O동위소조성δ~(18)O위21.4‰～24.4‰,여침적형규질암상문합,지시료정상해수침적성인.규화암구별우층상규질암적전형특정시구유고U이상적특정;라서사파방사상규화암구유교고적미량원소화희토원소함량(∑REE위18.8～96.9μg/g)여교저적Si、O동위색치(δ~(18)O화δ~(30)Si치분별위15.8‰화1.7‰);서부태지구교대잔여결구규화암구유교저미량원소화희토원소함량(∑REE위0.58～2.61μg/g)여교고적830Si(1.0‰～3.8‰)、δ~(18)O(21.6‰～27.0‰)치특정.분지동서부규화암적지구화학차이가능여규화류체적온도차이유관,라서사파방사상규화암규화온도상대경고;령일방면,규화과정대H_4~(30)SiO_4선택성교고,인이형성적교대석영구유교고적δ~(30)si치.근거고성4정규화암포과체균일온도여교대석영적O동위소치계산득도교대류체적δ~(18)O치위9.1‰.해치여산성암장수적δ~(30)O치상사,지시료규화류체가능래자우암장혹변질수;이δ~(18)O치(9.1‰)작위서부태지구규화류체적O동위소치,계산득도서부태지구규화암규화류체온도위101.3～158.5℃.근거석영O동위소온도계계산적규화류체온도정동고서저적추세,지시료규화류체가능래자태지동부.
Bedded siliceous rocks and cherts-bearing dolostone are widely distributed in Cambrian strata in Tarim Basin. The bedded siliceous rocks occur mainly as deep water sediments in the eastern Tarim Basin, and have been sampled from the Yingdong 2 well. The chert-bearing dolostones show a wide distribution in Cambrian dolostones of the whole Tarim Basin. In A1-Fe-Mn diagram, data for the bedded siliceous rocks fall within the normal seawater sedimentary field. In the crust-normalized trace element spider diagram, the bedded siliceous rocks show relatively smooth right-inclined curves, indicating sedimentary origin. Their silicon and oxygen isotope compositions are 0.9‰ - 1.4‰, and 21.4‰ - 24.4‰, respectively, coincident with those of the sedimentary siliceous rocks. The cherts in dolostone demonstrate higher U content in comparison with the bedded siliceous rocks. The stelliform cherts in Luoxi slope show high content of trace elements and low oxygen (15.8‰) and silicon (1.7‰) isotope compositions, as a result of high reaction temperature; on the contrary, the original texture remained cherts in the western platform demonstrate low trace and rare earth elements concentrations and high oxygen (21.6‰ -27.0‰)and silicon (1.0‰ - 3.8‰) isotope compositions, resulting from relatively low reaction temperature. Compared to other types of siliceous rocks, the cherts show relatively high δ~(30)Si value, maybe as a result of the selectivity of H_4~(30)SiO_4 during the silicatization process. Based on the homogeneous temperatures of fluid inclusions in quartz in Gueheng 4 well and the δ~(30)O values of cherts, the δ~(18)O value of silicatized fluid is calculated to be 9.1‰.Therefore, We can calculate the temperatures of silicatized fluid in western basin, and the temperatures range in 101.3 - 158.5 ℃. The temperatures show a decreasing trend from east to west in western platform, indicating that the hydrothermal fluids might have come from some eastern faults of the western platform.