地質燈籠 (Ge o’ the Lantern)

本文發表於《大眾科學》的前部落格網路，反映了作者的觀點，不一定代表《大眾科學》的觀點 (This article was published in 大眾科學’s former blog network and reflects the views of the author, not necessarily those of 大眾科學)

(萬聖節快樂！這篇文章最初發表於 En Tequila Es Verdad 部落格，於 2011 年，我認為大家可能會喜歡在這裡重刊。正常發帖將很快恢復，現在服裝狂潮已經結束，只剩下慶功派對了。很快再見！)

也被稱為地質燈籠，是普通南瓜燈籠的一個亞種。(Otherwise known as a geolantern, subspecies of the common jack o’ lantern.)

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是的，我給這個該死的東西上了色。相信我，你不會想讓我拿著刀靠近南瓜的。結果可能會讓你想起開膛手傑克犯罪現場的照片。(And yes, I painted the damned thing. Trust me, you don’t want to let me near a pumpkin with a knife. The results could put you in mind of Jack the Ripper crime scene photos.)

這一切都源於一系列有趣的事件的巧合。正如我所說，我非常不擅長雕刻南瓜，所以我本來打算放棄 Michael Klaas 的 “增生楔” 主題。沒有時間，工具，也沒有南瓜，對吧？即使如此，還在忙著寫 NaNoWriMo。但是，在星期天，在去車裡取汽水的路上，我看到了這個完美的、原始的南瓜，真是太美了，孤零零地坐在垃圾箱旁邊。所以我把它撿起來搬上樓。我對被遺棄的葫蘆科植物成員有種特別的喜愛。(This all came about through an interesting confluence of events. As I said, I am teh suck at pumpkin carving, so I was going to give Michael Klaas’s Accretionary Wedge topic a miss. Didn’t have time, tools, or a pumpkin, right? Busy doing NaNo, even so. But then, on Sunday, on the way out to the car to retrieve soda, I saw this beauty of a pristine pumpkin sitting forlornly by the dumpster. So I fetched it up the stairs. I have a soft spot in my heart for orphaned members of the squash family.)

嗯，我想。我可以把它變成一塊混合巖。(Hmm, I thought. I could turn it into a migmatite.)

然後 Volcanoclast 釋出了這張漂亮的檯面照片 (And then Volcanoclast posted this beaut of a countertop)

靈感就此而來。(And there it was. Inspiration.)

糟糕的是，我在繪畫方面幾乎和雕刻一樣糟糕，但儘管如此，結果還算不錯。(It’s too bad I suck almost as much at painting as I do carving, but it didn’t turn out too badly for all that.)

那張照片讓我著迷，並在 Twitter 上引發了一場對話。這是那種可能被當作花崗岩出售的東西，但這裡麵包含的內容遠不止這些。你有淺色的基質岩石，然後是這些顏色較深的包體。看起來像是長英質物質吞噬了鎂鐵質物質。這種情況有時會發生，當侵入的岩漿團抓住其他物質的碎片並將它們融入其中時。融入的碎片有時會融化，但並非總是如此。(That photo fascinated me and started a conversation on Twitter. It’s one of those things that probably got sold as granite, but there’s so much more going on here. You’ve got a pale host rock, and then these darker inclusions. It looks like something felsic gobbled up something mafic. That happens sometimes, where a mass of intruding magma grabs up bits of something else and incorporates them. The incorporated bits sometimes melt, but not always.)

然後 Lockwood 提到了反應邊。我認為這才是真正吸引我注意力的東西，因為我以前從未聽說過這些。(And then Lockwood mentioned reaction rinds. I think that’s what really grabbed my attention, because I hadn’t heard of those before.)

看到那些圍繞著藍灰色內部的較深岩石暈圈了嗎？那就是他所說的。從 Twitter 語翻譯成英語，以下是他所說的：“當捕虜岩/包體在岩漿環境中不穩定時，它會與岩漿發生反應，形成新的礦物。這些可以保護包體，和/或減緩反應速度，直到熔體在所有物質都反應完之前冷卻。這留下了一個幾乎原始的包體，周圍環繞著 ‘反應邊’。”(See those halos of darker rock around the blueish-gray interior? That’s what he was talking about. Translating from Twitterese to English, here’s what he said: “When a xenolith/inclusion isn’t stable in a magmatic environment, it reacts with the magma to form new minerals. These can protect the inclusion, and/or slow the reaction to the point where the melt cools before it all reacts. This leaves a mostly pristine inclusion surrounded by a ‘reaction rind.’”)

有問題的包體可能是鈣長石，根據 Ron 的說法，是輝長岩的一種變種。深色包體中可愛的、略帶藍色的顏色可能來自 拉長石 礦物。如果你還沒有機會欣賞它，去你當地的岩石商店買一些。轉動它。觀察它在壯麗的彩虹色中閃爍和發光。它太美了。(The inclusion in question is probably anorthosite, a variety of gabbro, according to Ron. The lovely sort-of blue in the dark inclusions probably results from the mineral labradorite. If you haven’t yet had the opportunity to enjoy some, get thee to your local rock shop and pick some up. Turn it round. Watch it shimmer and shine in a magnificent sort of iridescence. It’s gorgeous.)

Ron 不確定是什麼導致了反應邊中深沉而濃郁的棕色（或者如果你想要一個不那麼像葫蘆的同義詞來形容這種現象，也可以稱之為暈圈，儘管 “邊” 非常符合這個增生楔主題的精神，你不覺得嗎？）。可能是 角閃石。可能是 黑雲母。透過檯面的照片來確定這些事情並不總是可能的，無論照片多麼棒。我們可以拿一個手標本並確定地找出答案，但檯面所有者可能不太願意允許這樣做，即使是為了科學。(Ron’s not sure what’s causing the deep, rich brown color in the reaction rinds (or coronas, if you’d like a less gourd-like synonym for the phenomenon, though rind fits rather well with the spirit of this Accretionary Wedge theme, don’t you think?). Could be hornblende. Could be biotite. It’s not always possible to determine such things through a photograph of a countertop, no matter how awesome. We could grab a hand sample and find out for sure, but the countertop owner may not be entirely willing to allow that, even if it’s for science.)

所以，這就是啟發了一篇增生楔文章的照片，並開啟了一個全新的主題。未來請關注檯面地質學！並關注 Volcanoclast 的部落格。那裡有很多好東西，外加一個引人入勝的神秘檯面即將到來！(So, that’s the photo that inspired an Accretionary Wedge post and launched a whole new topic. Watch for countertop geology in the future! And watch Volcanoclast’s blog. Great stuff there, plus an intriguing mystery countertop to come!)

與此同時，我將留給你們一張貓與地質燈籠的兇殘照片，法語：chat meurtrier avec la geolanterne。(In the meantime, I’ll leave you with a photo of chat meurtrier avec la geolanterne.)

感謝 Volcanoclast、Lockwood DeWitt 和 Ron Schott 提供的靈感和幫助。(With gratitude to Volcanoclast, Lockwood DeWitt, and Ron Schott for their inspiration and assistance.)