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Working up high! The Peruvian Andes

Intro: The high Andes in central Peru is home to unbelievably high hills, ridiculous roads, remarkable little communities and funny furry animals. It is also home to beautiful geology and prospective ground for mineral exploration. I recently traversed the roads and hills in this energetic country, and learnt that things are a lot harder to do when you have to do it up high (e.g., > 4 km)! In this post I’ll share a bit of the landscapes and geology of central Peru, and what it is like working at altitude!

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Two Peruvian guides from the local community watching the horizon – central highlands, Peru

The Peruvian Andes mountains

South America, subduction, flat slab, flat-slab

Subduction along the west coast of South America with “flat-slab” areas outline in black boxes. From Hays et al., (2012) and Hu et al. (2016).

South America is pretty special in that it is one of the only places in the world that has had consistent subduction along the same coastline for hundreds of millions of years! The eastward subduction of the Nazca Plate (i.e., the Pacific Ocean) under South America is what created the Andes mountain chain (i.e., the longest mountain chain in the world) starting ~ 570 million years ago (e.g., Jordan et al., 1983; Stern, 2004). In areas along the coast of South America the angle of this subducting plate is shallow, known as “flat-slab” subduction. Here there is a compression in the crust, which is related to a lack of active volcanoes and a “surplus” of copper ± gold ± molybdenum ore deposits (e.g., Benavides-Cáceres,1999; Noble and McKee, 1999). For more information on this check out my posts on “The Andes, copper mines and volcanoes of Chile!” and “Hidden gold mines and stone forests of Northern Peru“.

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Ominous misty mountain of the central highlands of Peru

One of the most prominent and dominant rock groups of the high Andes mountains are Cretaceous sedimentary rocks of the Marañón fold-and-thrust belt. These were deposited in a basinal environment, which was later folded and contorted (sometimes referred to as thin-skinned deformation), possibly due to the flattening of the subducting plate (Mégard, 1987; Ramos and Aleman, 2000; Scherrenberg et al., 2014).

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Geology and the Marañón fold-thrust belt of Peru (Scherrenberg et al., 2014)

The Marañón fold-thrust belt was intruded in the Miocene by volcanic and plutonic rocks. The plutonic rocks are evident in the Cordillera Blanca and consist of large granitic mountain range. The volcanics are less visually striking, but still compose lots of the very high mountains, and are typically the host rock unit to more epithermal-type gold deposits in the region (e.g., as in the north near Cajamarca). Towards the coast of Peru the geology is dominated by another large batholith, but this one is much older (Cretaceous, ~ 150 to 65 million years) and is known as the Coastal Batholith.

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Mountains part of the Cordillera Blanca. Folded rocks beneath are Jurassic-aged (~160 m.y.) sediments of the Marañón fold-and-thrust belt and the mountain peaks are Neogene-aged (~10 my.) granitic intrusion (~ 5 km high)!

 

Working in the Andes

Areas we like to explore in, alas, happen to be very very high up. Some of the places I was in are close to 5,000 metres above sea level! Things work a bit differently when you are so high up… Simply walking up several metres on a steep hill suddenly becomes a struggle for breath! The lack of oxygen and lower pressure can (and typically does for foreigners) induce altitude sickness, resulting in headaches, nausea and other symptoms. It can be more severe and life-threatening though, so it is important to take it seriously! I was lucky and only got a mild-case of it with a headache, but apparently it affects you differently each time you go up, so figures crossed for the next time!

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Nevado de Rajuntay (5,475 m) – central highlands of Peru

Another thing unique to the Andes, and spotted quite often working at high altitude, are funny furry creatures. These are llamas, alpaca and vicuñas, which are all members of the camelid family and usually live at over 4,000 m! They are all famous for their soft wool which typically composes Peruvian garments. Vicuña wool is the softest and rarest as they are only wild and can be shorn every 3 years.

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Lots and lots of alpaca on a hill – central highlands of Peru

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La vicuña de Peru!

Final thoughts:

There are many unique things about Peru, and the central highlands offers exposure to lots of them. Driving through the little towns and communities, and the crazy pencil-thin roads on the steep mountain sides, make you really appreciate how what would be a very challenging thing (i.e., living up here) comes natural to the locals Peruvian of the central highlands. The landscapes in the central highlands of Peru can be both ominous and alluring, making it a challenging but rewarding place to explore… with heights that can literally take your breath away!

-Stephanie

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A soccer field in a community located very high up in the central highlands of Peru

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Stairway to… more steps? Located in the town of Cabana in central highlands of Peru

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Local guides on horses during exploration work in the central highlands of Peru

Peru, Trujillo, Chan Chan, Marking, historic site,

Friezes of the Chan Chan historic site in Trujillo, Peru

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A mountain lake and a distant storm (it can go from summer to winter pretty quick in the high Andes of Peru)

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7 Comments

  1. Peter Ahlstrom

    Wow! Must be more than twice as many alpacas as we’ve ever seen in an antelope herd (about 50).
    And that’s high! we live just under 3 km (just over 6000 feet, about 20 air miles west of the Rocky Mtn Continental Divide).
    We do enjoy getting out and “rockhounding” (not geologists, but we like it, and I grew up near an iron mining town.) 2 weekends ago my daughter and I were out some 60 miles from the nearest gas station, and found a tiny vivid green something in one of our samples. Might be either copper or turquoise; don’t know. (A few years ago our daughter and son were out there again, that time 80 or 90 miles from that gas station, and found a group of anthills just filled with grains of hematite. Only, according to the geologic maps we’ve seen, there should be no hematite within more than 100 miles of there – just sedimentary rock. But looks like the ants haven’t seen those maps!)

    Very interesting; very good pics. Keep it up. I’ve gotten more & more impressed with the University of Tasmania.

  2. Marina

    Beautiful photos once again. Thanks for sharing!

  3. Sandy Barton

    Love your blog and photos. I’ve always been interested in geology and plate tectonics and you make it all look so awesome!

    • Thank you very much Sandy, glad I can make it look awesome for you 😉

  4. Billy

    I can’t wait for watching a video about this trip! Always a pleasure to read more about geology!