内蒙古狼山-渣尔泰山中元古代被动陆缘裂陷槽裂解过程中的火山活动及其示踪意义  

Sinsedimentry volcanic activities in the cracking process of the Mesoproterozoic aulacogen of passive continental margin in Langshan-Zhaertai area,Inner Mongolia,and its indicating significance.

作　　者：彭润民[1] 翟裕生[1] 韩雪峰 王志刚 王建平[1] 刘家军[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室和地下信息探测技术与仪器教育部重点实验室,北京100083 [2]内蒙古化工地质勘查院,呼和浩特430074

出　　处：《岩石学报》2007年第5期1007-1017,共11页Acta Petrologica Sinica

基　　金：国家重点基础研究发展计划项目(编号2006CB403503);国家自然科学基金项目(批准号:40572064);国家自然科学重点基金项目(批准号:40234051);内蒙古自治区地质勘查招标项目(编号:2004-01-KY2);高等学校学科创新引智计划(B07011)联合资助

摘　　要：狼山-渣尔泰山中元古代被动陆缘裂陷槽内产有炭窑口、东升庙、霍各乞和甲生盘等海底喷流-沉积铅锌铜铁硫化物矿床。它在裂解过程中产生了明显的间歇性海底火山喷发。已分别在霍各乞、东升庙和炭窑口矿床容矿岩组中已找到岩性不同、并具有变余斑状或聚斑状或显微球粒结构、变余杏仁构造的海相火山岩与凝灰岩层,它们是确认该裂陷槽裂解过程的有效标志。依据(1)西部炭窑口矿区容矿岩组中发育钾质"双峰式"火山岩,其基性火山岩的K_2O(4.23～5.93%)>Na_2O (2.15～3.14%)、Na_2O+K_2O=6.51～8.08%、长石斑晶为钠长石(No.=2.8～7.2),酸性火山岩的K_2O(6.22～4.83%)>Na_2O(2.78～3.87%)、Na_2O+K_2O=8.63～9.00%、长石斑晶为钠长石(No.=0.2～0.7)、长石微晶主要为钾长石;(2)东升庙矿区则发育钠质"双峰式"火山岩,其基性火山岩的Na_2O(3.84～4.30%)>K_2O(2.49～3.80%)、Na_2O+K_2O=6.44～7.92%、长石斑晶为更长石(No.=11～25),酸性火山岩的Na_2O(3.64～5.31%)>K_2O(1.19～2.75%)、Na_2O+K_2O=6.28～7.68%,长石斑晶与基质均为钠长石(No.=0～1.1);(3)霍各乞矿区发育基性火山岩,其Na_2O(1.36～3.78%)>K_2O (0.30～2.16%),Na_2O+K_2O=2.03～4.09%;(4)炭窑口、东升庙与霍各乞矿床三矿区火山岩的稀土元素与微量元素蛛网图的标准化曲线有相似性和显著差别;(5)炭窑口、东各庙和霍各乞矿区基性火山岩的Sm-Nd模式年龄依次为1857～1877Ma和2006～2132Ma、1740～1867Ma、1486～1606Ma;(6)容矿岩组中有多层凝灰岩与火山碎屑及少量含火山碎屑的矿石,再结合该裂陷槽内各矿床的铅同位素模式年龄和甲生盘矿区只有少量凝灰质夹层,可以揭示该裂陷槽在中元古代的不均匀裂解过程,表现出从西部炭窑口→东升庙→东部的甲生盘一带先后裂解、狼山南侧早于北侧裂解以及从狼山→渣尔泰山同沉积期火山活动由明显→微弱的明显变化趋势。The Mesoproterozoic aulacogen of passive continental margin of Langshan-Zhaertai area hosts Tanyaokou, Dongshengmiao, Hougeqi and Jiashengpan hydrothermal sedimentary Pd-Zn-Cu-Fe sulfide deposits. Synsedimentary submarine volcano intermittently erupted in the breakup process of the aulacogen in the Mesoproterozoic. Different lithologic characters of volcanic rocks with blastoporphyritic and blasto-glomeroporphyritic and micro-spherulitic textures as well as blasto-amygdaloidal structure have already been discovered in the host succession in Huogeqi, Dongshengmiao and Tanyaokou deposits. They are the remarkable indicator horizon to recognise the breakup process of the anlacogen. It is revealed that the aulacogen had been unevenly cracked and expanded in the Mesoproterozoic based on the following features and facts： （ 1 ） Potassic bimoda volcanic rocks occurred in Tanyaokou. The basic volcanic rocks＇ K2O （4.23% - 5.93% ） 〉 Na2O （ 2. 15 % - 3. 14% ） and Na2O ＋ K2O = 6.51% - 8.08 %. Feldspar phenocryst of it consists of albite（ An = 2.8 -7.2）. The acidic volcanic rocks＇ K2O （4.83 - 6.22% ） 〉 Na2O （ 2.78 - 3.87% ） and Na2O ＋ K2O = 8.63% - 9.00%. Feldspar phenocryst of it consists of albite （ An = 0.2 - 0.7 ）, but feldspar microlite phenocryst of it mainly consists of potassium feldspar. （2）Sodic bimodal volcanic rocks occurred in Dongshengmiao. The basic volcanic rocks＇ Na20 （3. 84% - 4.30% ） 〉 K2 O（2.49% - 3.80% ） and Na2O ＋ K2O = 6.44% - 7.92%. Feldspar phenocryst of it consists of oligoclase （ An = 11 - 25）. The acidic volcanic rocks＇ Na2O（3.64% - 5.31% ） 〉 K2O（ 1. 19% - 2.75% ） and Na2O ＋ K2O = 6.28% - 7.68%. Both feldspar phenocryst and microlite consist of albites（ An =0 - 1.1 ）. （3） Only meta-basic volcanic rock occurred in Hougeqi. Its Na2O （1.36% -3.78%） 〉K2O（0.30% -2. 16%） and Na2O ＋K2O=2.03% -4.09%; （4） Distribution patterns of Ree and trace elements of the volcanic rocks of Tanyaokou, Dongshengmiao and Hou

关 键 词：同沉积期火山活动 中元古代裂陷槽 不均匀裂解 被动陆缘 华北地台北缘西段 

分 类 号：P542[天文地球—构造地质学] P611.1[天文地球—地质学]