摘要
辽北清原地区在时空上有系统地发育了三个太古亩地体：浑河以南的小莱河花岗岩-绿岩带（ＸＧＧＢ）、浑河以北的清原花岗岩-绿岩带（ＱＧＧＢ）和在ＱＧＧＢ东北部出露的景家沟麻粒岩-片麻岩区（ＪＧＧＲ）。绿岩带中火山岩组合在ＸＧＧＢ中以双峰式岩套为特征，而在（ＱＧＧＢ中以连续的钙碱性系列为特征。ＸＧＧＢ中斜长角门岩全岩Ｓｍ－Ｎｄ等时线年龄为３０１８±２０Ｍａ，Ｎｄ（ｔ）＝＋０．１９±０．１７，ＴＤＭ＝３３４７～３７３５Ｍａ，而ＱＧＧＢ中的斜长角闪岩全岩Ｓｍ～Ｎｄ等时线年龄为２８８４±４８Ｍａ，∈Ｎｄ（ｔ）＝＋２．６１±０．４１，ＴＤＭ＝２９３８～２９９２Ｍａ。ＪＧＧＲ中黑云麻粒岩的Ｒｂ－Ｓｒ等时线年龄为２９９４±３２５Ｍａ，可能代表变质年龄，表明其形成在ＸＧＧＢ之前。综合研究表明辽北地区太古亩地质演化模式很可能为：ＪＧＧＢ代表了古中太古代古陆的残骸，ＸＧＧＢ于中太古代形成在这个古陆边缘的裂谷盆地内，ＱＧＧＢ则形成在新太古代的大陆边缘岛弧环境，并于新太古代晚期与ＸＧＧＢ拼贴。在此陆一弧碰撞过程中，ＱＧＧＢ逆冲推覆于ＪＧＧＲ之上，后者由于后期的伸展作用而出露于地表。成矿作用是地质演化的组成部分。
Three distinct Archean terrains, including the Xiaolaihe granite--greenstone terrain(XGGT) to the south of Hun river, the Qingyuan granite-greenstone terrain (QGGT) to theNorth of Hun river and the Jingiiagou granulite-gneiss terrain (JGGT) occurring as a tectonicwindow in QGGT, developed systematically in space and time in the Qingyuan areas of northernLiaoning Province, China are recognized. The volcanic assemblages in XGGT are characterized bybimodal suite. But those in QGGT feature successive calc-alkali series. The amphibolite fromXGGT has a whole rock isochron Sm-Nd age of 3018 ±Ma with Nd(t) = + 0. 19 ±0. 17, TDm= 3347-3735Ma. In contrast, the amphibolite from QGGT has a whole rock isochron Sm-Ndage of 2844 ±48Ma with∈Nd = ±2. 61± 0. 4, TDM = 2938 -2992Ma. An isochron Rb-Sr age of2924 ±325Ma gained from biotite granulite samples in JGGT is interpreted as a metarnorphic age,indicating that JGGT was formed before XGGT.considering these datas along with other studies, a geologic evolution model is suggested forthe area. The JGGT probably is a Paleoarchean microcontinent, based on the edge of which, theXGGT was formed in a rift basin in the Mesoarchean. The QGGT was developed in island-arcenvironment in the Neoarchean and was accreted with XGGT in the Neoarchean. During thecontinent-arc collision, the QGGT thrusted onto the JGGT, which exposed to supracrust bysubseguent extensional process.The mineralizations are the integral parts of the geological developent. The banded ironformations in XGGT and QGGT as well as synvolcanic massive sulfide deposits in QGGT wereformed accompanying with the deposition of greenstone successions. The Child mineralization suchas the Nanlongwangmiao sulfidic disseminated gold deposit was developed during the continent-arccollision.
出处
《前寒武纪研究进展》
1997年第3期1-10,共10页
Progress in Precambrian Research
基金
"八五"地矿部科技攻关项目!85-01-002-02
关键词
太古宙
绿岩带
构造演化
成矿作用
矿床成矿
Archean, Tectonic Evolution, Metallogenesis, Qingyuan Area, China
