大地构造与成矿学
大地構造與成礦學
대지구조여성광학
GETECTONICA ET METALLOGENIA
2015年
4期
555-570
,共16页
高金尉%吴时国%彭学超%董冬冬%范建柯%贾连凯%周金扬
高金尉%吳時國%彭學超%董鼕鼕%範建柯%賈連凱%週金颺
고금위%오시국%팽학초%동동동%범건가%가련개%주금양
被动大陆边缘%洋陆转换带%珠江口盆地%西北巴拉望盆地-礼乐盆地%差异伸展
被動大陸邊緣%洋陸轉換帶%珠江口盆地%西北巴拉望盆地-禮樂盆地%差異伸展
피동대륙변연%양륙전환대%주강구분지%서북파랍망분지-례악분지%차이신전
passive margins%Continent-Ocean Transition%Pearl River Mouth Basin%NW Palawan-Liyue Basin%differential extension
南海被动大陆边缘洋陆转换带与典型洋陆转换带相比有其特殊性,南海共轭被动陆缘的构造运动、火山活动以及海底地形的差异表明南、北洋陆转换带具有不同的构造特征。本文利用多条多道地震反射剖面和重力异常数据,研究南海共轭被动陆缘洋陆转换带构造特征差异性,探讨南海被动陆缘的类型和伸展模式。南海北部陆缘洋陆转换带可以划分为两种类型:一类以前缘铲状断块为界与洋壳区分,发育有裂陷期断陷、火山带(埋藏海山带)和不十分发育的向海倾的掀斜断块带;另一类则以海山为界,发育裂陷期断陷、宽缓的低凸起和火山或海山。深反射地震特征显示出了下地壳高速层的存在。南部以裂陷期断陷和明显的向海倾的掀斜断块为特征,以前缘铲式断层为界与洋壳区分。自由空间重力异常由陆向海从高异常值过渡为低异常值再到高异常值,预示着地壳由陆壳→过渡壳→洋壳的变化。结果表明,南海共轭被动陆缘更可能属于非火山型被动大陆边缘,其洋陆转换带的构造差异主要受岩石圈差异伸展变形控制。
南海被動大陸邊緣洋陸轉換帶與典型洋陸轉換帶相比有其特殊性,南海共軛被動陸緣的構造運動、火山活動以及海底地形的差異錶明南、北洋陸轉換帶具有不同的構造特徵。本文利用多條多道地震反射剖麵和重力異常數據,研究南海共軛被動陸緣洋陸轉換帶構造特徵差異性,探討南海被動陸緣的類型和伸展模式。南海北部陸緣洋陸轉換帶可以劃分為兩種類型:一類以前緣鏟狀斷塊為界與洋殼區分,髮育有裂陷期斷陷、火山帶(埋藏海山帶)和不十分髮育的嚮海傾的掀斜斷塊帶;另一類則以海山為界,髮育裂陷期斷陷、寬緩的低凸起和火山或海山。深反射地震特徵顯示齣瞭下地殼高速層的存在。南部以裂陷期斷陷和明顯的嚮海傾的掀斜斷塊為特徵,以前緣鏟式斷層為界與洋殼區分。自由空間重力異常由陸嚮海從高異常值過渡為低異常值再到高異常值,預示著地殼由陸殼→過渡殼→洋殼的變化。結果錶明,南海共軛被動陸緣更可能屬于非火山型被動大陸邊緣,其洋陸轉換帶的構造差異主要受巖石圈差異伸展變形控製。
남해피동대륙변연양륙전환대여전형양륙전환대상비유기특수성,남해공액피동륙연적구조운동、화산활동이급해저지형적차이표명남、북양륙전환대구유불동적구조특정。본문이용다조다도지진반사부면화중력이상수거,연구남해공액피동륙연양륙전환대구조특정차이성,탐토남해피동륙연적류형화신전모식。남해북부륙연양륙전환대가이화분위량충류형:일류이전연산상단괴위계여양각구분,발육유렬함기단함、화산대(매장해산대)화불십분발육적향해경적흔사단괴대;령일류칙이해산위계,발육렬함기단함、관완적저철기화화산혹해산。심반사지진특정현시출료하지각고속층적존재。남부이렬함기단함화명현적향해경적흔사단괴위특정,이전연산식단층위계여양각구분。자유공간중력이상유륙향해종고이상치과도위저이상치재도고이상치,예시착지각유륙각→과도각→양각적변화。결과표명,남해공액피동륙연경가능속우비화산형피동대륙변연,기양륙전환대적구조차이주요수암석권차이신전변형공제。
Compared with typical passive margins, the South China Sea (SCS) has its particular characteristics in the Continent-Ocean Transition zone (COT) at the conjugate margins. Several tectonic events and volcanic activities occurred in the SCS, and differentials of seafloor topographies show that COTs at the northern and southern margins have diverse structures. Based on several crustal-scale multi-channel seismic reflection profiles and gravity anomaly data, this paper analyses the structures of the COT at the conjugate passive margins of the SCS and discuss the pattern and extensional mechanism. The COT was bounded by shelf slope-break at the landward, whereas the COT at the northern margin can be divided into two types according to the seaward boundary. One was distinguished from oceanic crust with frontier listric normal fault, and composed of syn-rift depressions with gentle highs, volcanic zone (buried seamounts) and not well developed rotated fault blocks mainly dip seaward. The other type was bounded by seamount, and characterized as syn-rift depressions, broad and gentle high and volcano or seamount. Two sets of strong reflection events in the deep seismic reflection profile indicate the existing of High Velocity Layer. In contrast, the COT at the southern margin was bounded by frontier listric normal fault, and occurred as syn-rift depressions, while the obvious rotated fault blocks mainly dip seaward which possibly merged into a detachment fault in the deep crust. Free air gravity anomaly shows that the anomaly values varied from high in the typical continental crust to low in the transitional crust then to high again in the oceanic crust. Results show that the SCS conjugate passive margins highly close to the magma-poor passive margins. The lithospheric differential extensional deformation controlled the structures of COT at the conjugate margins of the SCS.