АНУ-ын Геологийн албаны судлаачид далайн ёроолоос олборлосон сульфидын агууламжтай дээжүүд агаарт гармагцаа исэлдэж, өндөр хэмд хүрдэг болохыг илрүүлсэн нь далайн гүний олборлолтын аюулгүй байдалд шинэ сорилт болж байна.
АНУ-ын Геологийн алба (USGS), Далайн эрчим хүчний удирдлагын товчоо (BOEM) болон Далай, агаар мандлын үндэсний захиргаа (NOAA) хамтран 2022 онд Орегон-Калифорнийн эрэг орчмын “Escanaba Trough” хэсгээс 57 ширхэг чулуулгийн дээж цуглуулжээ. Судлаачид эдгээр дээжийг лабораторид хөлдөөж, нунтаглах явцад хоёр дээж нь аяндаа шатаж, 100 хэмээс дээш халуун ялгаруулсан байна.
Шинжилгээгээр эдгээр чулуулаг нь гол төлөв нанокристалл марказит буюу төмрийн сульфидын нэгдлээс тогтдог болохыг тогтоожээ. Уг эрдэс нь хүчилтөрөгчийн нөлөөнд маш тогтворгүй бөгөөд нунтаглах, бутлах зэрэг механик үйлчлэл болон химийн урвалын улмаас өөрөө халах процесс явагддаг байна.
Энэхүү үзэгдэл нь далайн гүний сульфидын ордуудыг олборлох үед хөлөг онгоцон дээр гэнэтийн гал түймэр гарах эрсдэлтэйг сануулж байна. Судлаачид далайн ёроолын эрдсүүд хуурай газрын ашигт малтмалаас эрс ялгаатай шинж чанартай тул ирээдүйн олборлолтын үйл ажиллагаанд аюулгүй байдлын тусгай дүрэм журам шаардлагатай гэж дүгнэжээ.
Scientific Reports сэтгүүлд нийтлэгдсэн энэхүү урьдчилсан судалгааны үр дүн нь далайн гүний экосистемийн эрсдэл болон олборлолтын салбарын аюулгүй байдлын асуудалд шинэ анхаарал хандуулж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
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Researchers hoping to tap the metal wealth of the ocean floor have stumbled onto an unexpected hazard: some seafloor rocks can ignite on their own once they reach the surface. Two samples collected in 2022 did exactly that, reaching temperatures above 100 °C and oxidizing completely.
The finding comes from scientists at the United States Geological Survey (USGS), who are flagging it as a possible problem for any future mining of seafloor massive sulfide deposits. Their work, published in Scientific Reports, is being shared early, before full editing, so the public can see it sooner.
The International Seabed Authority has granted exploration contracts for sulfide minerals on two deep-sea ridges, the Northern Mid-Atlantic Ridge and the Southwest Indian Ridge. Mining hasn’t started, but when it does, there is reason to tread cautiously.
A Sample Collection That Took a Surprising Turn
The rocks came from the Escanaba Trough, which sits in the US Exclusive Economic Zone off the Oregon–California border. Hydrothermal activity there has created deposits rich in metals such as copper, zinc, and iron. The USGS collected the material in 2022 in collaboration with the Bureau of Ocean Energy Management (BOEM) and the National Oceanic and Atmospheric Administration (NOAA).
Using a remotely operated vehicle, the team gathered 57 hydrothermal rock samples from four regions of the trough. Most contained metal sulfides as a major mineral. Then came the lab work. When researchers freeze-dried and crushed the samples, two of them spontaneously combusted.
Sulfide minerals are special because they can contain precious metals like gold, silver, copper, or zinc. They can also spontaneously combust.
What Made These Rocks Different?
One possible explanation involved petroleum. Heavy sedimentation in the deep ocean can promote the formation of hydrothermally derived petroleum, which can be hidden within metal sulfide minerals and, on land, can self-heat. To pin down the cause, the study compared the mineralogy, chemical composition, and thermal behavior of the 2022 samples.
Tar and petroleum didn’t seem to be the problem. Instead, the self-combusting rocks were made mostly of nanocrystalline marcasite, a form of iron sulfide that appears to be especially unstable in the presence of oxygen. Heat and mechanochemical forces like crushing, breaking, and grinding can supply the energy to start oxidation, and oxidation can lead to self-heating.
That doesn’t mean every rock on the ocean floor containing marcasite is a hazard. It is, however, a potential danger that could help shape safety regulations for a new industry.
Why It Matters for Mining Safety
The practical worry is what happens during extraction. According to the USGS, rocks brought to the surface would experience conditions “dramatically different from those on the seafloor,” including exposure to oxygen and changes in temperature, pressure, and moisture. Those changes, the agency adds, could affect how sulfide minerals react and how much heat they generate.
The authors say that producing heat through exothermic reactions has not been investigated in seafloor massive sulfide deposits, yet it has the potential to cause “rapid onset fires on ships,” according to the recent article. The USGS describes the issue as a “potential hazard that could merit special consideration” if deep-sea mining of these deposits moves forward.
A USGS press release goes further, saying some of these rocks have physical and chemical properties that could make them “behave very differently from comparable mineral deposits mined on land.”
Fire isn’t the only concern hanging over the industry, either. Many environmentalists worry that this burgeoning sector may be the last straw for ocean ecosystems that are already at risk.
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