بررسي هيدروژئوشيميايي و ژئوترمومتري چشمه هاي آب گرم سيستم ژئوترمال منطقۀ شوط- ماكو

Hydrogeochemistry investigation and geothermometry of hot spring in the Shoot-Maku geothermal system

ﻫﺪف از اﯾﻦ ﭘﮋوﻫﺶ، ﺑﺮرﺳﯽ ﺧﺼﻮﺻﯿﺎت ﻫﯿﺪروژﺋﻮﺷﯿﻤﯿﺎﯾﯽ ﭼﺸﻤﻪ ﻫﺎي آب ﮔﺮم ﻣﺮﺑﻮط ﺑﻪ ﻣﯿﺪان زﻣـﯿﻦ ﮔﺮﻣـﺎﯾﯽ ﺧـﻮي - ﻣـﺎﮐﻮ، ﺗﺄﺛﯿﺮ واﺣﺪﻫﺎي ﺳﻨﮕﯽ و ﻧﻘﺶ ﺳﯿﺎﻻت ﻫﯿﺪروﺗﺮﻣﺎل ﺑﺮ اﻓﺰاﯾﺶ ﻏﻠﻈﺖ ﻋﻨﺎﺻﺮ در ﺗﺮﮐﯿﺐ آب ﭼﺸﻤﻪ ﻫﺎ و ﺗﺨﻤﯿﻦ دﻣﺎي ﻣﺨﺰن ﺑـﻮد ﮐﻪ ﺑﺮاي اﯾﻦ ﻣﻨﻈﻮر در ﺷﻬﺮﯾﻮرﻣﺎه 1397 از آب ﭼﺸﻤﻪ ﻫﺎي ﮔﺮم و ﺳﺮد ﻣﻨﻄﻘﮥ ﻣﻄﺎﻟﻌﻪ ﺷﺪه ﻧﻤﻮﻧﻪ ﺑـﺮداري ﺻـﻮرت ﮔﺮﻓـﺖ. ﻧﺘـﺎﯾﺞ ﺑﺮرﺳﯽ ﻫﺎي ﻫﯿﺪروﺷﯿﻤﯿﺎﯾﯽ ﻧﺸﺎن ﻣﯽ دﻫﺪ آب ﭼﺸﻤﻪ ﻫﺎ ﺟﺰء ردة آب ﻫﺎي ﻣﺤﺼﻮر و ﮐﻢ ﻋﻤﻖ ﺑﺎ ﺗﯿﭗ ﺑﯽ ﮐﺮﺑﻨﺎﺗﮥ ﺳﺪﯾﮏ اﺳـﺖ، ﺑـ ﻪ ﻃﻮري ﮐﻪ ﻣﻘﺪار Na و HCO3 ﺑﻪ ﺗﺮﺗﯿﺐ 736 و 2122 ﻣﯿﻠﯽ ﮔﺮم ﺑﺮ ﻟﯿﺘﺮ ﻣـﯽ رﺳـﺪ . ﻧﺘـﺎﯾﺞ ﺑﺮرﺳـﯽ ﻧﺴـﺒﺖ ﻫـﺎي ﻣﺨﺘﻠـﻒ ﯾـﻮﻧﯽ و ﻧﻤﻮدار ﻫﺎي ﻫﯿﺪروژﺋﻮﺷﯿﻤﯿﺎﯾﯽ ﻧﺸﺎن داد زﯾﺎد ﺑﻮدن ﻏﻠﻈﺖ ﻋﻨﺎﺻﺮ در ﺗﺮﮐﯿﺐ آب ﭼﺸﻤﻪ ﺑﯿﺸﺘﺮ ﻣﺮﺑﻮط ﺑﻪ ﺗﺄﺛﯿﺮ ﺳﻨﮓ ﻫﺎي ﻣﯿﺰﺑـﺎن و ﻓﺮاﯾﻨﺪ ﺗﻌﻮﯾﺾ ﯾﻮﻧﯽ اﺳﺖ. در ﭼﺸﻤﻪ ﻫـﺎي آب ﮔـﺮم ﺑـﺎ ﻏﻠﻈـ ﺖ زﯾـﺎد HCO3, Na و ﻋﻨﺎﺻـﺮ ﻓﺮﻋـﯽ As و B ﺑـﺎ ﻣﻘـﺎدﯾﺮ 1/47 و 0/7ﻣﯿﻠﯽ ﮔﺮم ﺑﺮ ﻟﯿﺘﺮ، ﺑﻪ دﻟﯿﻞ ﻧﺒﻮد ﺳﻨﮓ ﻫﺎي ﺗﺒﺨﯿﺮي، ﻫﻤﭽﻨﯿﻦ ﺑﻪ دﻟﯿﻞ ﺣﻀﻮر ﺗﻮده ﻫﺎي ﮔﺮم ﻣﺎﮔﻤﺎﯾﯽ در اﻋﻤـﺎق، ﻣﻨﺸـ ﺄ اﯾـﻦ ﯾﻮن ﻫﺎ ﻣﯽ ﺗﻮاﻧﺪ ﺑﻪ ﺟﺪاﯾﺶ آن ﻫﺎ از ﺳﯿﺴﺘﻢ ﻣﺎﮔﻤﺎﯾﯽ و ﻫﯿﺪروﺗﺮﻣﺎل ﻣﺮﺗﺒﻂ ﺑﺎﺷﺪ. آب ﻫﺎي ﺣﺮارﺗﯽ ﻣﻨﻄﻘﮥ ﻣﻄﺎﻟﻌﻪ ﺷـﺪه ﺑـﺮ اﺳـﺎس دﯾﺎﮔﺮام Na-K-Mg ﺟﺰء آب ﻫﺎي ﻧﺎﺑﺎﻟﻎ اﺳﺖ، ﺑﻨﺎﺑﺮاﯾﻦ ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ از ژﺋﻮﺗﺮﻣﻮﻣﺘﺮ ﻫﺎي ﮐﺎﺗﯿﻮﻧﯽ ﺑﺎ دﻣﺎي ﻣﺨـﺰن ﺑـﯿﻦ 22 ﺗـﺎ 667 درﺟﮥ ﺳﺎﻧﺘﯽ ﮔﺮاد ﻧﻤﯽ ﺗﻮاﻧﺪ از ﺻﺤﺖ و دﻗﺖ ﮐﺎﻓﯽ ﺑﺮﺧﻮردار ﺑﺎﺷﺪ. ﺑﺮ اﺳﺎس ﻧﺘﺎﯾﺞ ﺣﺎﺻـﻞ از ژﺋﻮﺗﺮﻣﻮﻣﺘﺮﻫـﺎي ﺳـﯿﻠﯿﺲ، ﺷـﺎﺧﺺ اﺷﺒﺎﻋﯿﺖ ﮐﺎﻧﯽ ﻫﺎي ﮐﻮارﺗﺰ و ﮐﻠﺴﺪوﻧﯽ و ﻣﺪل اﺧﺘﻼط آﻧﺘﺎﻟﭙﯽ ﺳﯿﻠﯿﺲ دﻣﺎي ﻣﺨﺰن ﺧﯿﻠﯽ زﯾﺎد ﻧﯿﺴﺖ و ﺣﺪود 70 ﺗـﺎ 78 درﺟـ سﺎﻧﺘﯽ ﮔﺮاد ﺑﺮآورد ﻣﯽ ﺷﻮد.

The aim of this study is to investigate the hydrogeochemical characteristics of hot water springs of Khoy-Maku geothermal field, the effect of different rocks, the role of hydrothermal fluids on increasing the concentration of ions and elements in springs and estimating the reservoir equilibrium temperature. For this purpose, water samples were taken from hot and cold springs in september 2018. The results show that this water is confined and shallow and in them a water type is Na-HCO3. In springs Na and HCO3 are 736 and 2122 mg/l, respectively. Results of ion ratios, hydrogeochemical diagrams show that the high concentration of ions in the water are related to the effect of host rocks and ion exchange. Hot water springs have high Na, HCO3, and As and B are 1.47 and 0.7 mg/l, respectively. There are no evaporative rocks in the study area, therefore, the source of ions cannot be only attributed to the effect of rocks. Due to the presence of heat magmatic bodies in the depths, the high concentration of some elements, can be related to their separation from magmatic and hydrothermal systems. According Na-K-Mg diagram the thermal waters were immature waters. Therefore, the use of cation geothermometers to estimate the depth temperature of the geothermal reservoir in the region between 22 to 667 °C, can not be accurate enough. Based on silica geothermometers, mineral saturation index and enthalpy–silica mixing model, reservoir temperature was not very high and estimated in the range of 70 to 78°C.