青海共和—贵德盆地增强型地热系统(干热岩)地质—地球物理特征
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摘要
青海共和—贵德盆地处在秦岭—昆仑造山带"秦昆岔口",是新生代断陷盆地。盆缘活动断裂、岩浆岩发育,水热活动强烈、温泉密集,超过60℃的温泉6处,最高可达93.5℃,超过当地沸点(92℃)为沸泉。盆地内地温场高,据地热钻井揭露见花岗岩的三个孔,QR1孔深969 m,孔底温度为70℃,DR1孔深1 455 m,孔底温度87℃,R2孔深1 709.56 m,孔底温度可达97℃,地温梯度高达6～7℃/100 m,是正常地温梯度2倍,地热增温随深度增大而升高,推测3 000 m温度可达150～200℃,重力低异常推断基底凹陷与可控源音频大地电磁测深、地震反射波勘探推断基底界面深度不一致,并有磁异常对应,又经钻探证实。由此认为重、磁异常为花岗岩引起。花岗岩为燕山期,进入花岗岩钻孔深部有热无水,故认为盆地可能存在干热岩。
The Gonghe-Guide basin of Qinghai Province is located in a Cenozoic graben basin of the Qingling-Kunlun orogenic belt,where there are many active faults,magmatites and intense hydrothermal activities.There are 6 hot springs whose temperatures are over 60 ℃,with the hottest one reaching 93.5 ℃,which is beyond the local boiling point(92 ℃) and is hence defined as a boiling spring.The geothermal field is high in this basin.According to three geothermal drill holes that uncovered granite,the drill hole named QR1 969 m in depth exposed 70 ℃ at the bottom,the drill hole named DR1 1 455 m in depth exposed 87 ℃ in the bottom,the drill hole named R2 1 709.56 m in depth even exposed 97 ℃ at the bottom.Geothermal gradient is up to 6-7 ℃ per 100 meter,being two times of the normal gradient.The geothermal warming increases with the depth,and the authors inferred that the temperature in the depth of 3000 m is about 150 to 200 ℃.The basement depth inferred by low gravity anomaly is not consistent with the CSAMT and seismic reflection results.With corresponding magnetic anomaly and drilling evidence,the authors believe that the gravity and magnetic anomaly is caused by Yanshanian granite.As the deep drill holes intersect heat but no water,the authors hold that there may exist hot dry rock as the heat source of this basin.
The Gonghe-Guide basin of Qinghai Province is located in a Cenozoic graben basin of the Qingling-Kunlun orogenic belt,where there are many active faults,magmatites and intense hydrothermal activities.There are 6 hot springs whose temperatures are over 60 ℃,with the hottest one reaching 93.5 ℃,which is beyond the local boiling point(92 ℃) and is hence defined as a boiling spring.The geothermal field is high in this basin.According to three geothermal drill holes that uncovered granite,the drill hole named QR1 969 m in depth exposed 70 ℃ at the bottom,the drill hole named DR1 1 455 m in depth exposed 87 ℃ in the bottom,the drill hole named R2 1 709.56 m in depth even exposed 97 ℃ at the bottom.Geothermal gradient is up to 6-7 ℃ per 100 meter,being two times of the normal gradient.The geothermal warming increases with the depth,and the authors inferred that the temperature in the depth of 3000 m is about 150 to 200 ℃.The basement depth inferred by low gravity anomaly is not consistent with the CSAMT and seismic reflection results.With corresponding magnetic anomaly and drilling evidence,the authors believe that the gravity and magnetic anomaly is caused by Yanshanian granite.As the deep drill holes intersect heat but no water,the authors hold that there may exist hot dry rock as the heat source of this basin.
引文
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[15]王斌,何世豪,李百祥.青海共和盆地地热资源分布特征兼述CSAMT在地热勘查中的作用[J].矿产与地质,2010,24(3):280-285.
[2]曾梅香,李俊.天津地区干热岩地热资源开发利用前景浅析[C]//郑克棪,潘小平,董颖.中国地热资源开发与保护研讨会论文集,北京:地质出板社,2007:56-51.
[3]孙贤恺,江苏泰州地区可能存在增强型地热系统(干热岩)[C]//郑克棪,田廷山,董颖.地热能的战略开发——2009国际地热协会西太平洋分会地热研讨会论文集,北京:地质出板社,2009:94-99.
[4]李福.海南岛干热岩地热发电选址研究[C]//郑克棪,田廷山,董颖.地热能的战略开发——2009国际地热协会西太平洋分会地热研讨会论文集,北京:地质出板社,2009:94-99.
[5]孙知新,李百祥,王志林.青海共和盆地存在干热岩可能性探讨[J].水文地质与工程地质,2011(2).
[6]石宝颐,张峻太.论秦昆构造带的共和“缺口”[J].青海地质,1982(3):21-29.
[7]姜春发,王宗起,李锦轶,等.中央造山带开合构造[M].北京:地质出版社,2000:107-110.
[8]王吉玉,张兴鲁.青海共和盆地的挽近构造运动[J].西北地质科技情报,1979(1):25-29.
[9]袁道阳,张培震,刘小龙,等.青海鄂拉山断裂带晚第四纪构造活动及其所反映的青藏高原东北缘的变形机制[J].地学前缘,2004,11(4):393-402.
[10]熊亮萍,汪集旸,庞忠和.漳州热田的对流热流和传导热流的研究[J].地球物理学报,1990,33(1):702-711.
[11]廖志杰.新西兰那法热田重力资料的地质意义[G]//地热专辑:第二辑,北京:地质出版社,1989:259-263.
[12]郭万成,时兴海.青海省贵德县(盆地)地热资源的开发利用[J].水文地质与工程地质,2008(3).
[13]方斌,周训,梁四海.青海贵德县扎仓温泉特征及其开发利用[J].现代地质,2009(1).
[14]龙作元,薛国强,周楠楠.贵德盆地深部地热资源地球物理评价[J].地球物理学进展,2009(6).
[15]王斌,何世豪,李百祥.青海共和盆地地热资源分布特征兼述CSAMT在地热勘查中的作用[J].矿产与地质,2010,24(3):280-285.
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