结构特征与石油地质条件研究中国塔里木盆地南部褶皱冲断带原文.docx

1、结构特征与石油地质条件研究中国塔里木盆地南部褶皱冲断带原文 .Abstract The west Kunlun fold-thrust belt (WKFTB) and the Altun fold-thrust belt (AFTB) are respectively located in the southern margin of the Tarim basin, NW China. The analyses of typical structures and regional dynamics of the fold-thrust belts reveal their differen

2、t structural and pe-troleum features and mechanisms. WKFTB differs from AFTB by abundant fault一related folds andtriangles zones, and was formed by northward extrusion of the west Kunlun orogen. AFTB was affected synchronously by northward extrusion of the Altun orogen and the sinistral strike-slippi

3、ng of the Altun Fault, so it is characterized by the minor scale and the monotonous structural styles.The Aqike anticline and the Aqike fault, of which the strikes are orthogonal to the strike of the fold-thrust belts, are regarded as the adjustive structures between both of the fold-thrust belts.Th

4、e Tarim basin, NW China, neighbors respec-lively on the west Kunlun orogen and the Altun orogenin south. The Altun area was regarded formerly as apart of the Tarim basin and named Altun Fault-Up-lift. Now the Altun area is regarded as an Early Pa-leozoic orogen because of discoveries of the ophiolit

5、e,eclogue and high-ultrahigh pressure metamorphicrocks within the Altun areas一9. The Yechen andHetian sags are located in the northern piedmont of thewest Kunlun orogen, and the Minfeng and Ruoqiangsags are located in the northern piedmont of the Altunorogen (fig. 1). Both of the west Kunlun fold-th

6、rust belt(WKFTB) and the Altun fold-thrust belt (AFTB) arelocated in the southern edge of the Tarim basin, butWKFTB is more attractive than AFTB because of theirdifferent structural features and petroleum potentials,so many of researchers have paid their attentions toWKFTB6. AFTB has rarely been res

7、earched. On the basis of the comparison of the typicalstructural sections of both the fold-thrust belts, thepaper tries to reveal their different structural features,transition relationship between them, dynamicsmechanisms and petroleum geologyThe oil-gas pools of WKFTB develop mainly in the faulted

8、-related anticline traps, but the oil-gaspools of AFTB develop mainly in the low fault-block and anticlines traps related with the -leo一uplifts. There are different exploration countermeasures for both of the fold-thrust belts.Keywords: Tarim, west Kunlun orogen, Altun orogen, fold-thrust belt, stru

9、ctural features, petroleum geology.D01: 10.1360/04zd00251 Structural feature of the fold-thrust belts Both of the fold-thrust belts have differenttural scopes (fig. 1) and styles (fig. 2).truc-Structural features ofWKFTB WKFTB is characterized by the following fivestructural features: (1) Imbricate

10、thrusts. Such thrustsdevelop in the south of Fusha, where the Froterozoicmetamorphic rocks thrust northwards (Fig. 2(a). (2)Fault-propagation folds. In the Fusha and Kekeya ofthe Yechen sag, as a result of the accommodation ofthe displacement on the underlying thrusts, thefault-propagation folds wer

11、e formed in the overlyingstrata (fig. 2(a). (3) Back-thrusts and triangle zones.The Sangzhu triangle zone is clearly reflected in theseismic lines, and the superposition of the Permianstrata has been proved by the wells (fig. 2(b). (4)Fault-bend folds. The fold in the south of Hetian is atypical fau

12、lt-bend fold (fig. 2(c). (5) Buried thrusts. Inthe north of the revealable Tiebei fault口in fig. 1),the thrust are buried, and the Hetian fault(in fig. 1) is one of the largest buried thrusts, of which the van-guard is about 40 km away from the Tiebei fault. Theburied thrusts are related to the four

13、series of regionaldetachment levels, i.e. gypsum-argillaceous rocks inthe base of Cambrian, base (75-206 m in thickness)and top (400-670 m in thickness) argillaceous rocksof Lower Permian Pusige Formation (P,p) and thegypsum (0-136 m in thickness) of Paleocene Aer-tashi Formation (E,a). The variable

14、 depth of the de-tachment levels along the strike of the fold-thrust beltis one of the main reasons for the different structuralstyles . The above-mentioned structural styles dividedWKFTB along its strike (almost E-W) into Kekeya,Sangzhu-Duwa and Hetiannan segments04, andthe oblique thrust (strike-s

15、lip) faults between variousarcuate segments are the special intraplate deformationproduct of the Southwest Tarim foreland basin0. WKFTB takes its shape during the large-scalethrusting since Eocene0. In Kekeya, from south tonorm expose rusna, neKeya ana Human anncmes mturn. From south to north, the a

16、ge of the folded stratabecomes younger gradually, and the scale of the foldsminishes gradually. The fact that Miocene strata dieout in the Fusha and Sangzhu anticlines suggests thatboth of the anticlines have their rudimentary shapes inthe end of Oligocene. Pliocene Atushi Formation (NZa)in the nort

17、hern limb of the Kekeya anticline dies outsouthwards, so the Kekeya anticline was formed in theend of Miocene. A series of strata overlying Plioceneof the Guman anticline die out, indicate that the Gi-man anticline was formed after Plioceneb. In thewestern bank of the River Sangzhu, the Upper Car-bo

18、niferous limestone occurs as nappe outlier on thePliocene Atushi Formation (NZa). The southern edgefault of WKFTB (Tiebei fault) transects the upperPleistocene (Q3) conglomerate in the Duwa area. Themiddle Pleistocene (Q2) overlies on the Xiyu Forma-lion with clear unconformity in the foreland of th

19、ewest Kunlun orogen. All of the above-mentioned geo-logical facts show that the large-scale thrusting ofWKFTB took place during Miocene and Pleistocene. WKFTB is probably active now because (1)Holocene strata in Kekeya are folded0; (2) in someseismic lines, the triangle shape of the growth strata in

20、Pleistocene has not completed. So the vanguard faultof WKFTB (Hetian fault) is active.1.2 Structural features of AFTB AFTB is less developed than WKFTB because oftwo reasons: (1) thrusts and its displacement areminor; and (2) fault-related folds and triangle zone donot exist (fig. 2(d), (e). The wid

21、th of AFTB is obviously less than that ofWKFTB (fig. 1), such also is reflected by the landformin the foreland of the Altun orogen. Strong contrast ofthe landform between the Altun orogen and Min-feng-Ruoqiang sag occurs along the main fault of theAltun fault system. The higher topography of the Al-

22、tun Mountaim contrasts with flatter topography of thesags. Between the Altun Mountain and sags there is anarrow ramp dipping northwards, which is made up ofthe AFTB. In the Jianggesayi area, Froterozoic felsicgneiss thrust over Jurassic coal-bearing strata (fig.2(e). Jurassic and overlying strata co

23、nsist of a gentleramp about 3km in width. Figures 2(d) and (e) make clear that in the north-ern foreland of the Altun orogen exist not only thestrike-slip faults, but also the fold-thrust belt. Becauseof the limited width along the thrusting direction, thefault-related folds and triangle zone genera

24、lly cannotbe developed. Minfeng and Ruoqiang sags occurred as afault-subsidence basin during Jurassic, and Jurassicconglomerate overlapped southwards on the Frotero-zoic. The large-scale rise of the east Kunlun Mts. andAltun Mts. in Cenozoic results in thrusting northwardsin their northern foreland,

25、 and the unconformity be-tween Jurassic and Proterozoic is over-turned, andJurassic-Pliocene strata dip northwards steeply. Theapproximate horizontal unconformity between Pleis-tocene and its underlying strata (fig. 2(e) indicatesthat thrusting took mainly place in the middle-laterPliocene. Similar

26、to WKFTB, AFTB is also active now. Inthe aerial and satellitic image, the accordant left-de-flexion of the rivers from the Altun Mts. along themain Altun fault indicates the active strike-slipping inthe fault. As the fault is transpression, it should thrustnorthwards while left strike-slipping.L Aq1

27、Ke tranSltlOn structure between W lir l iiand AFTBFeatures and mechanism of the Aqike structureThe Aqike structure is a special unit in the south-edge of the Tarim basin, and consists of AqikeJln2.erfaulted anticline and Aqike fault (fig. 1). Aqike faultedanticline is transected by the northern edge

28、 fault ofTiekelike, and its axis approximate to south-northstrike plunges northwards. The Silurian(?)low-gradedmetamorphic rocks expose in its core, and are overlainby the conglomerate, sandstone-bearing gravel of theupper Devonian Qizilafu Formation (D3q). The west-ern limb consists of Upper Carbon

29、iferous, Permian,Lower Cretaceous and Paleogene is well exposed. Theeastern limb is transected by Aqike fault, and Carbon-iferous, Permian and Paleogene expose discontinu-ously along the fault. The strata of the western limbdip 400-600, but the strata of the eastern limb dipsteeply or overturnedly.

30、The axial plane dippingwestwards reflects the extrusion from west to east.Because that the Wuqia Group(E3-N,) wq)is involvedin the fold, the anticline was formed in Plio-Gene-Pleistocene. Aqike fault located in the easternlimb near the core of the Aqike anticline dips west-wards with 650-700, and be

31、longs to a strike-slipthrust with approximate S-N strike. According to theseismic data, the Aqike fault also lies concealednorthwards about 40 km (fig. 1). The particularity ofthe Aqike structure consists in its strike orthogonal tothe fold-thrust belts rather than paralleling to thefold-thrust belt

32、. The Aqike structure results from the interactionof the different dynamic mechanisms of WKFTB andAFTB. The structure is formed in two stages: (1)Pliocene-Pleistocene, WKFTB in the western side ofthe Aqike structure thrusts toward NNE, while the sin-istral strike-slipping of the Altun fault system in the