摘要
沉积物源分析是认识盆山演化的重要途径。天山南麓库车地陷不同剖面的砾岩碎屑、砂岩骨架颗粒、碎屑重矿物组分显示,它们的成熟度及演变时限总体可以类比,表明其成因演化主要受控于物源区——(古)天山的构造活动与造山作用。对碎屑沉积记录的综合分析进一步指示,天山物源总体以“再旋回造山带”类型为特征,其演变细节包括五期:①早三叠世古天山继承石炭纪以来的构造挤压和隆升,物源岩石类型主要为沉积岩、中高级变质岩,以“碰撞造山和褶皱冲断带”及“混合造山带”类型为特征;②中三叠世-中侏罗世构造活动较弱,代表高成熟度的“锆石-金红石-电气石”重矿物组合发育,主要物源岩石类型包括变质岩和酸性火山岩,与“弧造山带”以及“混合造山带”类型关系密切;③晚侏罗世-白垩纪,天山开始新一轮的构造挤压隆升,物源岩石类型复杂;④第三纪(特别是中新世)构造挤压和隆升活动加强,稳定性极差的碎屑“角闪石- 辉石”组合增多,物源组分东西分异明显,西部沉积岩相对较多,物源构造属性趋向“碰撞造山和褶皱冲断带”;东部结晶岩相对较多,物源构造属性复杂或以“混合造山带”类型为特征;⑤上新世南天山强烈隆升和向南推进,与前一阶段相比沉积岩物源增多,但物源构造属性基本同上。第④⑤两个阶段砾岩层和不稳定碎屑组?
It is an important method to understand basin-range evolution through studying depositional provenances. Similar
evolutionary sequences of detrital maturity are found to exist in conglomerate clasts, sandstone framework grains and detrital heavy
minerals, respectively, from different profiles in the Kuqa depression along the south of the Tianshan, northwest China. The similarity
of those time-series profiles mainly resulted from tectonic activities and orogenesis of the provenance area, (ancestral) Tianshan. An
integrated research on clastic deposition in the Kuqa depression shows that the Tianshan provenances are characterized by the recycled
orogen type, whose evolutionary sequences may be divided into the following five phases: (1) succeeding to tectonic extrusion and
uplift regime since Middle Carboniferous, the ancestral Tianshan supplied provenances mainly consisting of sedimentary and middle-
high grade metamorphic rocks and characterized by the collision orogen and mixed orogenic sandstones types; (2) from Middle Triassic
to Middle Jurassic, with weak tectonic activity, provenances mainly consisting of metamorphic and acidic volcanic rocks attributed to
arc orogen and mixed orogenic sandstones types were developed, finally resulting in stable detrital heavy mineral assemblages,
constituted by zircon, rutile and tourmalin, in depositional records; (3) a new round of extrusion-uplift of the Tianshan began in Late
Jurassic and Early Cretaceous, which resulted in complex provenance types; (4) tectonic extrusion and uplift of the south Tianshan
were intensified during Paleocene-Miocene (especially Miocene), with an increasing contents of unstable detrital heavy minerals
consisting of hornblende and pyroxene, which resulted in provenances differentiation along the south of the Tianshan, that is, more
sedimentary rocks mainly attributed to the collision orogen and fold-thrust belt types occurred in west and more crystalline rocks
attributed to the mixed orogen type in east; and (5) more sedimentary provenances influenced the Pliocene clastic deposits, with
similar tectonic attributes to those of the phase four, under intensive uplift and southward (basinward) accretion of the south Tianshan.
It is also presented that the conglomerates and unstable detrital assemblages developed in the above fourth and fifth phases may be
influenced by acute climate oscillation as well as intensive uplift of the Tianshan.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2004年第3期655-666,共12页
Acta Petrologica Sinica
基金
国家重点基础研究发展规划(973)项目G1999043303课题资助
关键词
天山
库车坳陷
盆山系统
碎屑组分
物源
中-新生界
Tianshan
Kuqa depression
Basin-range system
Detrital composition
Provenance
Mesozic-Cenozoic
