by Vladimir ZNAMENSKY, Cand. Sc. (Geol. & Mineral.), RAS Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry (IGEM)

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The islands of the Main Kurile Chain (Kunashir, Iturup, Urup) and some of the Minor Chain (Shikotan, Zeieny, Polonsky, Anuchin, Yuri, Tanfilyev) are sites of unique natural phenomena. Apart from their salmon spawning- grounds and rich flora and fauna, they are the site of many active, ancient and "dormant" volcanoes. And it is these latter ones that are famous for their manifold hot springs - each being different, and sometimes very different, from its closest neighbor not only in its appearance, but in its therapeutic properties.

RAINBOW OF HOT SPRINGS

Major volcanic eruptions on the Kuriles are few and far between and not all of the local residents have had an opportunity of living through such an experience. But the "natives" are quite familiar with hot springs, or hydrotherms, of all shapes and sizes. Such springs are quite common at currently inactive volcanoes (what is known as the solfataric, fumarole or interparoxysmal stage - between two successive eruptions of lava, tuff or steam-and-gas mixture). As a rule, the interim periods of relative calm are tens and even hundreds of times longer than the eruptions. For example, the "handsome" Tyatya Mount on Kunashir "blew up" as far back as in 1812 and again in 1974 and has been silent ever since with only traces of fumarole activity in its crater. Other volcanoes on the same island (Golov-nina, Mendeleyeva, Ruruy) and northward Iturup (Berutarube, Kud-ryavy, Baransky) have never erupted in living memory, but have periods of intense hydrothermal activity.

The whole range of what we call contemporary hydroterms located on island chains framing the Pacific can be found on volcanoes located on the islands of Golovnin, Mendeleyev, Baransky and Kudryavy*. The only thing that's missing are grandiose outflows, like those in the Geysers' Valley** on Kamchatka, although "microgeysers" are still there. And there are fewer so-called sodium- chloride surface springs than in other regions. All of these hot water reservoirs can be tapped by simply drilling wells. Incidentally, in countries like the United States, New Zealand, Italy, Japan and Iceland thermal water sources are being used for generating electricity and for house heating. In other cases they are used for extracting metals and they also possess high concentrations of salts, above all sodium chloride.

One common feature of volcanoes with hydrothermal activities is the presence of either relatively young, or ancient calderas, or troughs in the earth crust, produced by strong volcanic explosions. Accumulated therein within a short span of time are mountain rocks and large volumes of water - up to the appearance of big lakes. In the subsequent course of development of such calderas residual magma is first squeezed out from earth's interior, forming at different depths intermediate sources of cubic kilometers in volume, or domes on the surface (Golovnin caldera). In the course of their subsequent geological development these troughs can turn into so-called stratovolcanoes or effusive- extrusive domes (Kipyashchaya and Medvezhya calderas on Iturup). It is this seepage from depth of viscous acid magma which causes convective warming of the surrounding rock and then the formation of hydrothermal solutions. Gas emitted by magma warms up the above water-bearing strata, producing fumarole water. Other types of hot springs, depending on the nature and mode of their formation, are called solfataric or mixed.

TYPES OF THERMAL WATER

I would like to distinguish four basic genetic types thereof which match in the main, by their origin and geo-chemical characteristics, the major items in the classification developed by Dr. Valery Ivanov of the RAS Institute of Water Problems.

First, there are the subneutral sodium-chloride (often with admixture of calcium ion and hydrocarbonate-ion), thermae, or hot springs, of regional propagation, which are commonly present at various depths and feature increased concentrations of boron, and sometimes of heavy metals, and other specific ions. Second, there are ultrapersilic (acidic) sulfate-chloride thermae - volcanogenic or fumarole, which mostly originate at depths, with sour gases dissolved - hydrogen sulfide, sulfur dioxide, haloid acids. Third, there are acidic or sour, and sometimes subneutral sulfide thermae; they are formed on the surface by the oxidation of hydrogen sulfide rising from the depths with the subsequent formation of sulfuric acid (as different from the first two, these thermae have low discharge, from hydrosolfataras (streams of transparent water or viscous mud) of different types which I shall be dwelling upon later. Finally, in the fourth place, there are subneutral and weakly acidic sulfate-chloride thermae of mixed formation produced during the con-

* See: V. Znamensky, "Unique Volcano on the Kuriles", Science in Russia, No. 4, 2000. - Ed .

** See: V. Ivanchenko, "The Pearl of Kamchatka", Science in Russia, No. 4, 1991 . -Ed.

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densation, neutralization or combination of different solutions; these often indicate the presence in the depths of reservoirs of very hot thermal water.

Now, let us consider some of the most typical hydrothermal systems of the Southern Kuriles in the direction from south-west to north-east.

BUBBLING LAKE, "SULFURIC" BEACH, "SINGING" FIELD

In the south of the Kunashir Island, in the Golovnin caldera some 4 km in diameter, after a volcanic eruption (some one min years ago) and subsidence of the surface, magma residue was incorporated in the beginning; not thrown out by the blast, this was later "squeezed out" from down below, forming numerous domes of 1 km ³ each. With the subsequent accumulation of water a huge lake - Goryacheye - was formed in the depression; formed on its bottom, as a result of fumarole activities and other processes, were layers of rather rich sulfur ores. Today this water is weakly sour by taste (pH5) and is very pleasant to take a dip in during summer. But shortly after there occurred an explosion in the center of the caldera, at the foot of one of the domes, and the crater was quickly filled with water. This is the way the small Lake Kipyashcheye was formed; sulfuric gases are still seeping through at its bottom and a 9-meter layer of stratified sulfur ore has been formed. Gases melt and saturate the deposited native sulfur which is floating up to the surface as foam, bubbles and lentils and is carried off through a narrow channel into Lake Goryacheye where a pleasant "sulfuric" beach has been formed. Bathing there almost every night are local bears which settled in this area after the establishment of the Kurilsky Wild Life Preserve. Water in the lake continues to accumulate and overflows through a narrow crack in the wall of the caldera gfving birth to the Ozernaya River, which is full of rapids and which has cut a deep canyon through the side of the Golovnin volcano.

The gases saturating Lake Kipyashcheye turn the water into a highly acidic solution (pH 2-3) from which transparent scales of the sulfate mineral alunite precipitate - together with black fine-grain iron sulfides and silica oxide. The water contains plenty

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of aluminum, iron and silicon from the dissolving surrounding rocks. Surface temperature in the lake is from 30 to 35 ⁰ C and reaches 90- 100 ⁰ C at places of gases discharge on the banks. A little below the surface the water has high levels of hydrogen sulfide and is completely void of oxygen. That is why one should take special care when bathing in the lake - your life will be at risk if you swim into an ascending hot current saturated with gas. And the hydrosolfataras located on the banks are all very different-hot and cold, acidic and alkaline. And there is also an alkaline spring which carries up to the surface and into the lake plenty of arsenic.

There are many solfataras on the slopes of the surrounding domes. For example, on the side of the Golovnin volcano dropping down to a pass between the island of Kunashir and Hokkaido there is a solfatar field, deeply cut into the relief, with isolated hydrosolfataras. The tall and almost vertical surrounding walls are crook-veined with meter-thick layers of calcium sulfate (anhydrite). And the local acoustics is such that even despite the roar of the solfataras and the bubbling of mud and water pots one can hear some music-like background sounds. Me and my colleagues in the expedition called this a "singing" field.

Located further down the slope of the volcano and on the very coast are the Alekhinskiye springs. There are tens of them there, but just a few with a high water discharge, including some typical sodium-chloride and ultra-sour bisulfate ones. The latter must be fed deep down below by volcanic gas, depositing on the surface silico-alunite sediments with sulfur. Years ago staff of a local hospital in the Alekhinsky village built on the bank wooden baths with easily regulated water temperature.

Some experts believe that the originally sour volcanic water along the coast is neutralized by natural circulation which accounts for a whole range of alkalinity values in springs scattered on the banks. Volcanic springs discharge on the sandy beaches, warming them up, and also on the lake bottom where there is a great variety of seaweeds and there are also colorful waterfowl. A big spring in the aforesaid village is channeled through pipes attached to some very fine baths. But the Alekhinskiye springs also include several which discharge into a pic-

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turesque bay, releasing into the water some arsenious minerals which are dangerous for health.

HOT SPRINGS OF MENDELEYEV VOLCANO

Located to the north-east of the Golovnin volcano, it features an entirely different structure. Apart from ancient relics, there is a better preserved young caldera and a summit crater with a recently embedded magmatic dome. Located on the slopes of the volcano are 3 solfataric fields. Vents of hot steam with a high content of hydrogen sulfide are located 50 to 100 meters above the hydrosolfatar fields, with water, and not steam, predominating in the post- volcanic process. And while native sulfur is precipitated during melting in plenty on the former, predominating on the latter is the formation of clays, crystallized sulfides and iron sulfides (pyrite, marcasite, jarosite). Due to an abundance of clays there occur landslides, changing the appearance of the surface.

The pyrite and native sulfur thus formed are rapidly oxidized by bacteria into sulfuric acid, and the remaining rock material is carried away by water - the well- known to tourists and very picturesque Kisly and Chetverikov springs and the Lesnaya River. The level of the solfatar and hydrosolfatar fields is constantly dropping due to the erosion and disintegration of the constituent rock, washing out of clay and silicon particles, and large volumes of other soluble matter. And, as a result, deeper strata or the volcano become exposed to sulfuric acid impact. And this is how "sulfite cirques" are produced which were originally mistaken by experts for lateral explosive craters.

The washing out and sinking of the surface in such cirques lays bare the earlier formed mineral facies. Thus on the north-eastern solfataric field of the Mendeleyev volcano pyrite deposit was exposed, consisting

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mainly of iron sulfide and silicon oxide in the form of opal. It is strewn with more recent sulfur veins and contains whole pockets of green crystalline sulfur. As for the more ancient minerals, we discovered sulfides of zinc, copper, silver, lead, mercury and other metals. Almost all of these finds were made by a member of our institute staff, Lev Lebedev, who devoted much time to studies of the mineralogy of the current processes at this volcano. Contributions to these studies were also made by some of my other colleagues - Alexander Zotov, Maria Dobrovolskaya, Nina Ozerova and Vassily Loginov.

Further down the slopes of Mendeleyev volcano one finds hot springs or a completely different kind - real fumaroles, formed at depth. These are the Nizhne-Mendeleyevskiye (Rosinka) and Verkhne-Doktorskiye springs, ultra- persilic sulfate-chloride ones with a temperature of 80-90 ⁰ C. They have a rather large discharge and are very popular with local residents and tourists. People dig ground baths which are usually washed out by flood water. The temperature at Rosinka is regulated by adding cold water from the Kisly spring and at the Verkhne-Doktorskiye springs there is no need for that since the water is pleasantly warm and forms natural baths and very beautiful waterfalls and drains with smooth depressions bathing in which is a real pleasure. Ultra-acid hot springs were opened up by a borehole at a depth of some 600 m. They feature a unique composition of secondary minerals, including sulfides, alunite, pyrophyllite and others, including rare minerals.

Located some two kilometers down the Doktorsky brook is a group of hot springs with unique curative properties-the Nizhne-Doktorskiye springs. Hydropathic clinics located there treat a range of ailments and disorders, skin conditions like eczema. This group also included some ultra-acid springs with a temperature of up to 60 ⁰ C (used for baths) and subneutral chloride- sodium ones (people drink this water for medicinal purposes). And one can find natural baths with warm mineral water all along the beach at low tides and these are very popular with local residents.

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Chloride-sodium springs have been opened up by drilling in this coastal area. The Goryacheplyazhskoye site of hot steam springs can discharge more than 5 kilos of dry steam per second at temperature of about 200 ⁰ C. This is the only such site in the Southern Kuriles which has been opened up for economic uses. Local specialists have gained experience of using steam hydroturbines with generators for producing electricity and this industry now continues to grow. Exhausted steam and steam from wells is used for domestic heating and in hothouses. The only problems are caused by the clogging of pipes with mineral deposits at reduced temperatures.

All of the above refers primarily to the north-eastern sector of the Mendeleyev volcano. And the solfataric and hydrosolfataric fields of its western and eastern sides are all of the same kind, although each of them has its own peculiarities and deserves detailed descriptions-the fine picturesque landscapes with jets of steam and water streaming up from the ground.

THE FAMOUS NESKUCHNENSKIYE

As on travels along the Okhotsk seacoast at Kunashir, moving from the Alekhinskiye springs to the north-east, one can not simply pass by the Tretyakovskiye, Valentinovskiye and the very popular Stolbovskiye springs with their medicinal "mud pots" where temporary baths can be dug up with any temperature in them. All springs here have mainly chloride-sodium water, generally like seawater, and evidently are not linked in any way with the local volcanoes. There are sites of fantastic beauty, such as a path leading from the main road to the Stolbovskiye springs. It passes through groves of silver firs, and relict yews, Glen spruce, velvet trees, magnolia and

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thick bamboo undergrowth. Further north along the coast one comes across the baths of the Dobry Klyuch springs which are very popular with the residents of Yuzhno-Kurilsk. They have the same kind of chloride-sodium water with a temperature of nearly 70 ⁰ C. And there are also the Severyankovskiye Springs, hiding in thick greenery along the river of the same name on the seacoast. But the broadest chemical spectrum can be found at the Neskuchnenskiye Springs in the north of Kunashir.

Here, at the foot of the Ruruy volcanic cluster, the acid Medvezhy Springs of solfataric type are located in steep scarps at the height of 200 to 250 m. The whole area is filled with a strong smell of hydrogen sulfide and sulfur dioxide, and specialists discovered here ancient and young deposits of sulfur and kies, or firestone. A hundred meters down, there are hydro-carbonate-chloride springs marked with fine pale-pink calcite sinters (calcium carbonate). Scattered along the coast, including the boulder-and-sand beaches, are many chloride- sodium springs which contain hydro-carbonate-ions and have considerable rates of discharge. If one has a spare water tank, or even a large enough wooden box, one can line it up with a plastic film and take a bath, filled with half of seawater and half with water from the spring. And you can enjoy this bath together with a fine view of the sea-quite a pleasure after the strain of hours of walking.

But one can hardly reach this place on foot without some special training and equipment. And it is much simpler to get to the Neskuchnenskiye Springs by sea, if, of course, the weather is good. And you can see in the Zalivnaya River some bears "fishing" with total disregard of any "intruders", such as poachers or fishing boats.

ON THE ITURUP

Deserving of our attention here, apart from the hydrothermal system of the Baransky volcano which 1 shall dwell upon a bit later, are the solfataras and hydrosolfataras of the Berutarube volcano, springs of Cape Urumpet, the Stokapskiye springs and sulfurous hot springs in calde-ra Novaya, located next to the only explored local deposit of vol-canogenic native sulfur. Further

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on there are the drilled Dachnye springs with water similar to that of the famous Yessentuki-4 springs in the Northern Caucasus. It has a pleasant taste and is consumed in large volumes by the locals. And there are small Narzan mineral water springs near the village of Gorny. Travelling over a distance of 17 km along the coast of the Kasatka Bay and passing the Goryachiye Klyuchi springs in the direction of Kurilsk, one can reach the Lososevye and Reidovskiye springs located on marshy terrain with hot medicinal muds. Years ago there were hot springs right on the coast near Kurilsk, but they have now run out. And the town residents have been rewarded with an 800-meter prospecting borehole which supplies them with a torrent of chloride-sodium water at 45 ⁰ C. Some primitive, but very popular, concrete baths were built on the site.

On the Grozny mountain range there is a very powerful fumarole located on top of a volcano by the same name. One can also see there the Machekha "crater" with very steep and loose walls of 400-500 m. I took the risk of going down there twice, but found just several small hot springlets and plenty of cold acidic water. My attention was also caught by a sulfur knoll some 20-meter high. Incidentally, one cannot really call Machekha a crater-it is but a very deep erosive cirque which appeared in the process of development of solfataric fields on the slope of one of the volcanoes of the Tebenkov mountain range. Also located there are the Rudnichnye warm springs which are but of little practical value.

BARANSKY VOLCANO

Of special interest today is the hydrothermal system of this volcano which boasts a vast energy potential and which is about to be tapped in the near future. It is also interesting because of a broad range of hot springs which includes all of the aforesaid types and which are extremely picturesque. Generally speaking, this place cannot be viewed in some narrow practical terms; it has to be cleared of debris left from hydrogeological prospecting and turned into an international holiday center also catering for tourists with a scholarly twist of mind.

The Baransky volcano is a complex volcanic massif which was

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formed in the vast Kipyashchaya caldera and the same name applies to the local hot springs. The caldera is strongly eroded and what remains of it are several arch ridges. River water and occasional Hoods have exposed its deep strata, including special gold-bearing rocks with transparent feldspar (adularia), pyrite, quartz and organic wastes.

The solfataric fields of Baransky volcano - Starozavodskoye, Verkhneye Fumarolnoye and Kipyashcheye - are developing according to the classical scheme, subsiding in relief and opening up new horizons of rock, modified at depth. In this process the upper several meters are enriched with clayey minerals - kaolinite and montmorillonite, with the levels of pyrite (kies) increasing with depth.

At first hydrogeologists thought that there are no hot steam occurrences here. But this view has been proved wrong by our Institute researchers who launched geological and hydrogeological explorations in this area in 1982-1983. At that time we had investigated practically all of the local mineral springs and found a special type of hot springs of what we call mixed composition which became our criterion in prospecting for overheated steam. And from the very first borehole, drilled at the estuary of the Kipyashchaya River, there gushed up from the depth of 220 m a jet of steam and gas at the pressure of 8 atm and it was saturated with bits and pieces of modified rock. The whole area sunk in clouds of white ash and mud. And we were hardly able to plug the borehole. It turned out later that there begins to accumulate on its bottom the mineral wairakite from the zeolite group (it indicated the hot steam sites in New Zealand and was named Wairakite after that area).

Later on hydrogeologists continued their ascent along the slope of

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the volcano and then decided to drill a borehole directly on the hydrosolfataric Starozavodskoye field, amidst the prevailing sour and ultrasour springs and mud pots. At the depth of 95 m they hit upon the heat carrier (we usually call so the steam-water mixture with a chloride-sodium composition) with a temperature of 195 ⁰ C. We later found out that such regionally occurring thermae form a dome over the source of heat - something that had been theoretically predicted by Vladimir Kononov (of the RAS Institute of Geology).

The most diverse outflows of thermae on the surface of the Baransky volcano are concentrated on the Starozavodskoye field of about 2 km ² . Located up above is a rather large sul-fur deposit, running down from which is cold sour sulfate water, and there are also warm springs the biggest of which is called Banny (a fine bath was built upon it) which is not too sour and one can enjoy bathing in it. And the whole of this area is specked with hundreds of water and mud pots, all kinds of steam jets and also smaller bubbling and seething "potties".

One very impressive local sight are brightly coloured thermophyllic algae: they perish in the shallow stream of boiling water, but are replaced with new ones again and again. And jets of water are so hot one can get a bad bum touching them.

In general, walking around that "field" could be dangerous, and in order to be on the safe side one better finds himself a local guide. All sorts of mud baths, volcanoes big and small, are constantly changing their shape and size, forming cave-ins and sinks in which new jets of hot mud spring up now and then. In some springs there accumulate sediments and encrustations of iron sulfides, and marcasite "replaces" grass, tree branches and other vegetation. Cold hydrosulfuric springs, flowing from under layers of sediments and rocks, run down in cascades. Their bottom is covered with sulfurite (fine dispersed variety of native milk of sulfur) of dazzling bright yellow color. One can see this everywhere - amidst the bright green verdure or brownish remains thereof.

An unforgettable impression is produced by the aforesaid Kipyashchaya River. It is only 1.5 km long and its temperature changes from more than 100 ⁰ C in the gryphon of one of the boiling mud pots down to 30 ⁰ C at the estuary where it flows into the Sernaya River - a big and grand current as measured on the Siberian scale.

The springs of the Kipyashchaya River are known under different names-some call them Golubye Ozera (blue lakes) because of the color of the seething water, or Zheltoye Oko (yellow eye) when the pots are framed with belts of bright- yellow sulfurite. The lakes are almost transparent, several meters deep, but plunging into their ultra-sour and superhot water can really be suicidal-human body can simply dissolve there without a trace. The seething river has a high discharge, carrying out daily some 60 tons of sulfuric acid and many other components, including a range of dissolved rare earths. Only two such streams are known in the world - Peito on Taiwan and Tamagawa in Japan.

As the water in the river runs down its course in cascades along the ravine and cools down, there appears on the bottom a sediment of hokutolite - a mineral of yellow or brown color consisting mainly of barium sulfate with a considerable (up to 15 percent) admixtures ofsul-fates of strontium, lead, calcium and rare earths sulfates (up to 2 percent by weight). One cannot bathe in this river for long because you suddenly feel your body as if filled with lead, your legs trembling under your own weight, and it takes one quite some time to get back into proper shape. And the sour water can hurt your eyes, although this water washes off all kinds of dirt and heals skin lesions.

Located somewhat higher than the Golubye Ozera lakes is the Kipyashcheye hydrosolfataric field with plenty of kettles, or pots, of sour superhot water. In many places, because of the dropping water level and the high temperature of seeping gases, the sulfur thus formed melts down and runs down in streaks tens and even hundreds of meters long.

BRIEF FAREWELL

So far our specialists have failed to find hydrothermal systems like the ones described on the more northward island of Urup which also belongs to the Big Kuriles arc. But they must be there nonetheless and in any case nearly ten groups of different thermae have been located along the coast and in the mountains. It may well be that a hydro-thermal system will be discovered between the three active volcanoes of central Urup - Trezubets, Berg and Kolokol. Located there on the slopes are very powerful Mariinskiye and Dariinskiye springs which belong to the category of ultrasour chloride-sulfate thermae with mixed cation composition with prevailing sodium ions.

One hopes that we shall see what one can call a civilized and planned development of the abundant resources of thermal waters of the Southern Kuriles, including a program of exciting tours and excursions, conduct of scientific experiments, and rational uses ofgeother-mal energy in the interests of the development of the Kuriles region.

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