Angelique Northcutt, Garrett Owen, Chris Perdue, Bo Price, - PowerPoint Presentation

Slide1

Angelique Northcutt, Garrett Owen, Chris Perdue, Bo Price, Tory Rogers

Geology of the Precambrian Sangre De Cristo Range and Picuris Mountains of New MexicoSlide2

Where are we going?Slide3

-The

Sangre de Cristo fault is a west dipping

fault

in New

Mexico -It forms the border between the Sangre de Cristo Mountains and the San Luis Basin.-The Sangre de Cristo fault extends from poncho Pass, Colorado to near where we’ll be in Taos, NM.

BackgroundSlide4

-

The

section we will be focused on extends from the San Pedro Mesa creek south to the intersection with the Embudo Fault at Rio del Rancho which is about 8 km south of Taos

.

-The Sangre de Cristo is part of the more recent Rio Grande Rift. -It is a normal fault that moves less than 0.2 mm/year.

Backgroun

dSlide5

-The

Basement rocks in this location are Precambrian in age.

-The

rocks of Colorado and Northern New Mexico are juvenile Volcanic- Plutonic, Ocean Arc rocks that are approximately 1.78 to 1.65 billion years old.

-In New Mexico these rocks have been assigned to the Yavapi and Mazatzal provinces.

-

These Rocks were deformed during 2 major Proterozoic

orogenies

.

HistorySlide6

-First

the Colorado Orogeny has a U-

Pb

date that goes through 1.78-1.75 Ga

.-It was a prolonged thermotectonic episode resulting from collision, subduction, and continued convergence.-This occurred along the

paleosuture

known as the Cheyenne

Belt along the

Archean Wyoming Province.

HistorySlide7

-Second

the Berthoud Orogeny has a U-

Pb

date that started 1.45

Ga and went through 1.40 Ga. -This was a thermo tectonic episode that produced NE trending ductile shear zones and related folds. -The mechanism powering this Orogeny was granitic plutonism

.

-This

Orogeny also formed many high grade metamorphic rocks through generally pervasive metamorphism.

HistorySlide8

-I

soclinal folding

-East-west strike

-Southward

dips (60-70 degrees)Pre-Cambrian rocksSlide9

-

2 major anticlines and 2 major

synclines

-Wave

lengths 1 to 2 miles-Doubly plunging (~20-30 degrees)

FoldsSlide10

Pilar Anticline

-Widely displaced by the Pilar-Vadito tear fault

-Slightly overturned to the north

-Axial plane dipping south (60 degrees)

Hondo Syncline

-Overturned

-Axial plane dips south (60-70 degrees)

-Eastern segment plunges 30-40W

-Western segment plunges 10-20E

FoldsSlide11

Copper Hill A

nticline

-

A

xial plane plunges 30-35W -N85W, 50W -Can be traced 9 miles east of Copper HillHarding

Syncline

-

S

tructural detail is obscure

-

S

trikes E-W

-

P

lunge

ranges 25-17NE

FoldsSlide12

-Abundant/wide variability in pre-Cambrian

rocks

-3 predominant

sets

-N10W to N10E (almost vertical)  -N50W to N70W (dipping steeply NE)  -N20E to N40E (dipping steeply SE)

JointingSlide13

-N-S joints followed almost

exclusively

by copper

ore-bearing

quartz veins-Mineralization after granitic intrusion-Harding pegmatite estimated

800myo

-Indicates time of jointing

JointingSlide14

-Conglomerate of the

Vadito

-Pebbles have

average axial ratio of 1:2:3-Shortest axis perpendicular to foliation-Some wedge-like shaped with apex oriented down the lineation-Pebbles in close contact have greater impacted shape

Stretched PebblesSlide15

Three Major Fault S

ystems

Picuris-Pecos

f

ault systemEmbudo transfer fault

Sangre de Cristo fault zoneSlide16

Picuris-Pecos Fault System

84 km long fault system consisting of five parallel fault zones:

Picuris-Pecos

-

Major crustal boundary juxtaposing two Proterozoic rock sequences: the Hondo Group and the Miranda GraniteLa Serna-East-down fault separating Miranda Granite and Picuris Formation

Miranda

-

North-striking strike slip fault

McGaffey

-West-down branching fault splay

Rio Grande del Rancho

-Kilometer-wide, west-down fault zoneSlide17

Embudo Fault Zone

Sinistral, antithetic transfer zone which forms border between the Española

Basin and the San Luis Basin

64 km long fault thought to be part of Jemez lineament Fault consists of two sections based on reversal of throwStrike of N60E

Sinistral net slip rate of .15 mm/yearSlide18

Sangre de Cristo Fault Zone

West-dipping normal fault that forms border between the Sangre de Cristo Mountains and the San Luis Basin

Beginning of Sangre de Cristo Fault forms the terminus of the Embudo fault

The southern area of the fault is divided into five sections. From north to south, the sections are:

- San Pedro Mesa - Urraca - Questa

The northern three strike north-south

- Hondo

Strikes N30W

-

Cañon

Strikes N20ESlide19

Aerial View of Faults in Taos RegionSlide20

The Hondo Group

-The Pilar Formation

-The Riconada Formation

-The Ortega Formation

The Vadito Formation

Pre-Cambrian Formations:Slide21

The Ortega Formation

Estimated 2,500 ft. thick

Gray to very light gray in color

Mostly Quartzite

Thin beds of sillmanite - kyanite gneiss

Bands of schistose with muscovite

TourmalineSlide22

Riconada Formation

-Richly micaceous foliated rocks

-

Consists of four distinct beds:

Andalusite-biotite Hornfels bed-

Muscovite and quartz matrix that contains biotite, nodular masses of quartz and andalusite

Staurolite Schist and Gneiss Bed- Soft and light gray in color micaceous matrix speckled with biotite, contains staurolite crystals

Staurolite

AndalusiteSlide23

The Riconada Formation

Quartzite bed – Grayish white in color, contains glassy- white and translucent quartzite

Muscovite-quartz-biotite-garnet Phyllite bed- Muscovite rich phyllite containing garnet crystals and biotite, sheen that ranges from pearly gray to greenishSlide24

Pilar Phyllite Formation

Estimated 2,300 ft. thick

Black to gray-black in color with a gray sheen

Contains muscovite flakes

Quartz veins

Limonite massesSlide25

Occupies

the southern 1/3 of the Picuris

Range

-

Named after the village of VaditoBest outcrops come from within a one-mile radius of the Harding Mine -Total thickness: 4,500 feet

Comprised

of a Lower Conglomerate Member and an Upper Schist Member

Vadito FormationSlide26

Marquenas

Formation

Total thickness: ~ 2,000

feet

Composed of Quartz Conglomerate and Quartzite, Felsites and Meta-andesites

Quartz conglomerate outcrops in a quarter-mile wide east-west belt near Picuris Canyon but grow sparser farther

east

Composed

of gray coarse to pebbly Quartzite with fine-grained micaceous quartzite matrix

Thickness

of the Quartz Conglomerate: 500 - 1,000 feet Slide27

Marquenas

Formation

Felsites occur to the east and west of the canyon but appear to pinch out to the west along the Ortega-Vadito

contact

Composed of meta-rhyolite that grades into coarser granite representing partial replacement by granite

Gray-white

to pink-white and has a dense felsitic texture with micas and feldspars

present

Thickness of the Felsites: 50-100 feetSlide28

Marquenas

Formation

Meta-andesites occur abundantly to the south and east of the Harding

mine

Greenish-gray to gray-black in color

Hornblende

occurs in all of these rocks as prisms and give the

variable darkness in color to themRocks show strong pleochroism in thin-section

.

Represent

thin-layered volcanic material of dacitic and andesitic compositionSlide29

Schist Member

Consists of a schist and phyllite composed of quartz-muscovite and a quartz-biotite

granulite

The schist is similar to the underlying conglomerate quartzite with more densely disseminated flakes of

muscovite Phyllite is a lustrous, silvery-gray rock with stubby biotite

porphyroblasts

Granulite is fine-grained, sandy, and crudely foliated with micaceous surfaces with flakes of

biotite

Thickness: At least 1,250 feet and no more than 2,500 feetSlide30

Amphibolites

The amphibolites found in the Vadito Formation are split into two zones based on lithology:

-

One

of the zones occurs in the Lower Conglomerate and one occurs in the Upper Schist

T

hese

amphibolites show effects of intrusion by granitic and pegmatitic

magmaThickness: 750 feet in Lower Conglomerate, and 1,250 feet in Upper SchistSlide31

Questions?