原文網址：www.sciencedaily.com/releases/2015/11/151103140444.htm

Diamonds may not be so rare as once thought

鑽石或許並不如之前認為的那般稀有

Chemical model shows a simpler deep Earth formation

化學模型顯示出鑽石在地球深處的簡易形成方法

Diamonds may not be as rare as once believed, but this finding in a new Johns Hopkins University research report won't mean deep discounts at local jewelry stores.

鑽石也許並不像之前咸信的如此稀有，然而這起約翰·霍普金斯大學新研究報告中的發現，並不代表你家附近珠寶店的鑽石價格會暴跌。

"Diamond formation in the deep Earth, the very deep Earth, may be a more common process than we thought," said Johns Hopkins geochemist Dimitri A. Sverjensky, whose article co-written with doctoral student Fang Huang appears today in the online journal Nature Communications. The report says the results 'constitute a new quantitative theory of diamond formation,' but that does not mean it will be easier to find gem-quality diamonds and bring them to market.

「鑽石於地球深處，非常非常深處形成的過程也許比我們認為得更常發生。」約翰·霍普金斯大學的地球化學家Dimitri A. Sverjensky說。他和他的博士班學生Fang Huang合撰的文章今日刊登於期刊《自然通訊》(Nature Communications)線上版。這篇報告寫道他們的結果「建構了一套可用來解釋鑽石如何形成的新型數量化理論」，但這並不代表找到並銷售寶石等級的鑽石會變得易如反掌。

For one thing, the prevalence of diamonds near the Earth's surface -- where they can be mined -- still depends on relatively rare volcanic magma eruptions that raise them from the depths where they form. For another, the diamonds being considered in these studies are not necessarily the stuff of engagement rings, unless the recipient is equipped with a microscope. Most are only a few microns across and are not visible to the unaided eye.

一方面來說，要在地表附近形成鑽石含量豐富而能供人類開採的礦藏，仍然要靠某些相當罕見，能將鑽石從它們形成的地球深處帶至地表的火山爆發事件。另一方面，這篇研究中所指的鑽石並不全然像訂婚鑽戒上的那般光彩奪目，除非收下的人配有顯微鏡。這些鑽石大都只有幾微米的大小，絕非肉眼可見。

Using a chemical model, Sverjensky and Huang found that these precious stones could be born in a natural chemical reaction that is simpler than the two main processes that up to now have been understood to produce diamonds. Specifically, their model -- yet to be tested with actual materials -- shows that diamonds can form with an increase in acidity during interaction between water and rock.

利用化學模擬方法，Sverjensky 和Huang發現這些珍稀的寶石能在某種自然發生的化學反應中形成，這種反應遠較目前為止所知，另外兩種形成鑽石的主要機制簡單許多。準確來說，雖然還未經實物驗證，他們的模型顯示水與岩石反應的過程中，酸度提高會使鑽石形成。

The common understanding up to now has been that diamonds are formed in the movement of fluid by the oxidation of methane or the chemical reduction of carbon dioxide. Oxidation results in a higher oxidation state, or a gain of electrons. Reduction means a lower oxidation state, and collectively the two are known as 'redox' reactions.

迄今，一般我們認為鑽石是由於液體流動的過程中，發生甲烷氧化或者二氧化碳還原而形成。氧化會提高物質的氧化態，或者可說是讓它失去電子；還原則會降低氧化碳，兩者通常合稱為氧化還原反應。

"It was always hard to explain why the redox reactions took place," said Sverjensky, a professor in the Morton K. Blaustein Department of Earth and Planetary Sciences in the university's Krieger School of Arts and Sciences. The reactions require different types of fluids to be moving through the rocks encountering environments with different oxidation states.

「要解釋氧化還原反應為何發生總是一件很難的事。」Sverjensky說，他是約翰·霍普金斯大學克里格藝術科學學院，地球與行星科學系的教授。這類反應需要不同流體在岩石中流動時，遇到氧化態有所差異的環境才會發生。

The new research showed that water could produce diamonds as its pH falls naturally -- that is, as it becomes more acidic -- while moving from one type of rock to another, Sverjensky said.

Sverjensky說，這項新研究顯示水在不同種類岩石之間流動時，在pH值自然下降(也就是變得更加酸性)的過程中，鑽石就會從中產生。

The finding is one of many in about the last 25 years that expands scientists' understanding of how pervasive diamonds may be, Sverjensky said.

Sverjensky說，包含此發現，科學家過去25年來已經從許多研究中愈加瞭解鑽石的分布其實是多麼廣泛。

"The more people look, the more they're finding diamonds in different rock types now," Sverjensky said. "I think everybody would agree there's more and more environments of diamond formation being discovered."

「人們愈去探討，他們就在愈多種岩石中發現鑽石。」Sverjensky說。「我想現在大家都同意會有愈來愈多的環境被發現有鑽石形成於其中。」

Nobody has yet put a number on the greater abundance of diamonds, but Sverjensky said scientists are working on that with chemical models. It's impossible to physically explore the great depths at which diamonds are created: roughly 90 to 120 miles below the Earth's surface at intense pressure and at temperatures about 1,650 to 2,000 degrees Fahrenheit.

雖然尚未有人發現由此成因而形成的豐富鑽石礦藏，Sverjensky說科學家可以利用化學模型來進行相關研究。目前人類還無法實際去探索鑽石形成的深度，它們位於地表之下140至200公里，在那裏壓力相當地大，而溫度可高達900至1100℃。

The deepest drilling exploration ever made was about 8 or 9 miles below the surface, he said.

他說，人類曾鑽到最深的地方也只不過是地表之下13至15公里。

If the study doesn't shake the diamond markets, it promises to help shed light on fluid movement in the deep Earth, which helps account for the carbon cycle on which all life on the planet depends.

即使這篇研究並沒有撼動鑽石市場，至少它肯定會讓我們對液體在地球深部是如何流動有更多的瞭解，而這與地球上所有生物依存的碳循環息息相關。

"Fluids are the key link between the shallow and the deep Earth," Sverjensky said. "That's why it's important."

「液體是連結地球深部和淺部的關鍵角色。」Sverjensky說。「這就是它為何如此重要的原因。」

This research was supported by grants from the Sloan Foundation through the Deep Carbon Observatory (Reservoirs and Fluxes and Extreme Physics and Chemistry programs) and by a U.S. Energy Department grant, DE-FG-02-96ER-14616.

本研究的贊助來自於斯隆基金會的深碳觀測計畫(Deep Carbon Observatory)下的子計畫，「儲量與通量」以及「極端物理化學條件」；另外一份則來自美國能源局計畫編號DE-FG-02-96ER-14616。

引用自：Johns Hopkins University. "Diamonds may not be so rare as once thought: Chemical model shows a simpler deep Earth formation." ScienceDaily. ScienceDaily, 3 November 2015.