一种可能的新碳酸岩类型:壳源成因碳酸岩  

A possible new carbonatite type:Cru st-derived carbonatite

作　　者：赵斌[1] 赵劲松[1] 汪劲草[1] 倪培[2] 李兆麟[3] 饶冰[2] 芦铁山[4] 邵俊智[4] 张重泽[1] 王冉[1] 彭卓伦[3] 涂湘林[1] 陈林丽[1] 

机构地区：[1]中国科学院广州地球化学研究所,广东广州510640 [2]南京大学内生金属矿床成矿机制研究国家重点实验室,江苏南京210093 [3]中山大学地质学系,广东广州510275 [4]大冶铁矿地质测量质量检测科,湖北大冶435006

出　　处：《地球化学》2004年第6期649-662,共14页Geochimica

基　　金：国家自然科学基金(40373019)

摘　　要：本文是对大冶铁矿床接触带“大理岩”及其中分布的“条带状辉石-石榴石大理岩”进行专门研究的阶段性结果。在野外观察到“大理岩”呈岩墙、岩枝和细脉侵入石英闪长岩。根据石准立等的趋势面分析资料,在深部,本矿区“大理岩”与石英闪长岩的接触带总是以突入石英闪长岩内为特征。在“大理岩”与灰岩接触带附近观察到大理岩粒度由于温度冷却快而变细和在“大理岩”中有灰岩残留体。“大理岩”本身的方解石粒度中部粗两侧细。本矿区的“大理岩”矿物结晶颗粒比长江中下游许多接触热变质形成的大理岩粗。“大理岩”内部浅色大理岩为白色,常具有定向的细条纹构造(可能为流动构造或构造事件引起的线性构造),局部产状变化急剧。在尖山矿段产在“大理岩”中的“条带状辉石-石榴石大理岩”,主要含辉石和石榴石条带,其条带走向与“大理岩”岩体延伸方向斜交,且与区内一组断裂构造有关。显微镜观察结果表明,在制备的约65块包裹体切片中均观察到熔融包裹体或流体-熔融包裹体及流体包裹体。包裹体加热实验结果显示,“大理岩”中方解石及“条带状辉石-石榴石大理岩”中的石榴子石和方解石中熔融包裹体接近均一的温度为880～1055℃,流体-熔融包裹体均一温度为645～740℃。“大理岩”及“条带状辉石-石榴石大理岩”的C?This paper is a stage result of specia l research for“marble”in contact of Daye iron deposit and“banded pyroxene-garnet marble”distributed in the“marble”.According to traditional theory th at the quartz diorite intruded into limestone first,then marble wa s formed by contact metamorphism and skarns were formed by metasomatism i n this area.However,finding of melt i nclusions in skarn minerals from skarns and in carbonate minerals from“marble”compelled us to consider the truth of traditional theory in respect of int erpretation for formations of skarn and marble in Daye Jianshan district.The“marbles”protrude into quartz diorite in the s hape of dyke,apophysis and veinlets.A quartz diorite xenolith with 1.5m ×3m in the“marble”from the ore block has been found.According to data of trend surface an alyses made by Shi Zhun-li,et al .the contact zone between“marble”and quartz diorite is always characterized by“marble”protruding into quartz diorite.It i s seen that in the vicinity of the contact between the“marble”and limestone(wall rock),grain size of the calcite from the“marble”became fine due to high cooling rate of temperatu re and the limestone xenoliths existed in the“marble”.Light-colored“marble”is white and usually has oriented-fine ribbon structure(it is possible for the flow structure or linear feature caused by tectonic event )and its occurrence locally sharply c hanged.“Banded pyroxene-garnet marble”occurred in the“marble”within Jianshan ore block is distrib uted in a narrow range and is mainly ch aracterized by pyroxene-garnet bands,the strike of which bevels the extension direction of the“marble”.The distribution of the“banded pyroxene-garnet marble”is related to a group of fault structu res in this area.The observations un der microscope indicate that melt inclusions,flui d-melt inclusions and fluid inclusions are almost found in 65inclusion t hin sections.The results of heating exp eriments show that melt inclusions i n the calcite from the

关 键 词：熔融包裹体 同位素 壳源成因碳酸岩 湖北省 

分 类 号：P594[天文地球—地球化学]